I think your counter-arguments are very bad. I thank you for sharing them here, because I don't think they reflect uncommon opinions at all, and I think they are too easily accepted without reflection.
With regards to the "defend to the death your right to say it" hyperbole, I agree that it is overstated. Furthermore, it is true that getting dis-invited from a tech conference does not involve losing the right to say anything; nor is the state punishing speech. However, it would be an error to overlook the fact that speech is being punished.
Yarvin would have been welcome at the conference had he not revealed his racist opinions in [what was intended to be] an unrelated forum. Those opinions revealed, he was unwelcome, without (as far as I can tell) any particular reference to his actual public behaviour. So as a practical matter, if the conference's reaction should be considered normative and appropriate, he had a right to say things... unless he wanted a career.
Now, you may well wish to argue that this reaction should indeed be normative and correct. However, I am not sure that you would be as comfortable with your actual words in another context. We could be discussing this in Russia in the 1950s, for instance, and agreeing that Yarvin shouldn't have kept his jewish-sounding last name if he wanted a career, or got forbid spoken about his anti-socialist economic views.
In such a case, our circumstances would have been very different, of course, and it is incredibly easy to draw broad distinctions between counter-factual racist fantasies and failing to disguise one's ethnic background. But the mechanism is the same, and here you are stating an indifference to --- defending, even --- the mechanism.
Another commentator writes that "kicking people out of your conference hands veto power to whomever determines what racism is and when something is racist."
It seems to me that if a popular arbiter of opinion about racism could mobilize a grassroots reaction against racism as they saw it, when they saw it, and when they felt like it; and if that grassroots reaction probably would not have occurred without their instigation: under those circumstances, this assertion would come quite close to being true.
Again, this is not something peculiar to racism, or fighting against racism, or any particular political struggle at all. It is a mechanism whereby interest groups influence the direction of public discourse and policy. Yet here --- despite the certainty that there are interest groups using such tactics, somewhere in the world, whose views are pure anathema to you --- you are not actually defending the fight for social justice and inclusion; instead, you defend the mechanism.
More realistically, I do not think that you intended to even do so much as that. Your reply at first reads as an announcement of indifference and antipathy to the author's concerns. A rejection of actual argumentation or discussion, in other words. (This itself, in case you might overlook it, is rather far from an inherently virtuous sort of response.)
However, your parenthetical comment does attempt to justify the mechanism, and the comment is notable in that it specifically rejects the protection of actual minorities, instead embracing a "market" determination of right or wrong: in other words, the nature of a protected minority is to be determined by the opinion of the general majority.
A third commentator complains about a sort of reverse-racism burden, in that the "straight white male" is doubly impacted, as both the target of discrimination, and as a target of discrimination who is not a member of "a protected class." I do not think that this is a very defensible argument. However, "accept that the world isn't perfect, and feel lucky you don't have it worse" is not any better.
At risk of beating a dead horse, one must in general ask oneself if the response defends the structure or the substance of the allegedly discriminatory circumstance. I will assume you can predict my response to this as an argument defending the discriminatory structure. Insofar as the response is a defense of the substance of the circumstance, then it seems to be implicitly appealing for deference and calling for restitution, of sorts, in that a hardship should be accepted in recognition of the hardships of others. This is a very powerful and emotionally appealing argument... when made to address apparent discrimination that arises out of minority protection. The 'Why The "Safe Area" Of The [Women's/LGBT/Native] Center Is Not Discriminatory' speech would be the typical example, in my experience.
Here, it is much less appealing, and also misses the point. Reading your response literally, one should infer that any member of an identifiable group ultimately needs to accept that "the world isn't perfect" and that they will face some degree of 'oppression'; they should protest against and fight that oppression only if it is too much oppression, or too deadly. I am almost certain that this is absolutely not something that you meant to say. I suspect that you meant to convey that you thought the commentator's experienced/feared discrimination was trivial and negligible.
This would be fine, as a response, but the attempt to convert it into a self-evident, justified response on this basis is very weak, and I feel that the problem is that you are trying to do the easy thing rather than the hard thing, and to end argument or dialog rather than invite it. "You can see this playing out in video games..." really? Straight white men are falling prey to reverse discrimination in video games? I would love to hear the commentator attempt to justify this view. It would be satisfactory enough, I think, to simply end discussion by responding that "this is ridiculous unless you feel like making a cogent argument to the contrary." Instead, however, you let it slide completely: you even accept the premise. I feel that if you were not intent on justifying [reverse] discrimination (because it is reverse[1]), and instead were concerned about discrimination period, you would not have missed the opportunity to talk about what does or does not constitute discrimination --- let alone missed the fact that this is a ridiculous, indefensible imagination of what discrimination is.
Finally, the commentator who writes that "my personal opinions would get me called racist, sexist, and homophobic by Marxist standards and I was exhausted by the political mask I had to assume just to find and keep work."
Again, structure, substance, escape_goat goes on for a paragraph or two here in a now-predictable manner, let's skip to the good part... suffering.
You are responding to someone reporting a sense of alienation and mental exhaustion specifically because they had to wear a 'mask' in the workplace. Your response is that you imagine that it was a lot easier for them to wear that mask than it would be for them to change their skin color, or gender, or age.
This seems obviously true, as those are very difficult things to change. It is also true that these visible, physical qualities have created barriers in the tech industry. But it leaves begging the question of whether anyone should be required to wear a mask, and under what circumstances. Is it wrong to discriminate against co-workers on the basis of the color of their skin, but not wrong to feel uncomfortable around them if they act "too black"? Is it okay to create a "non-homophobic" environment and then fire people for revealing their sexual orientation? I am thinking that perhaps there are some circumstances where you would not find "it's easier to wear a mask" to be a satisfactory response at all. Even though, yes, it's easier to wear a mask.
Similar to the case of the third commentator, but more problematically, your response is clearly predicated against the complainant because of their (white, straight, male) identity and whatever mixture of personal emotions, political views, or what-have-you that makes someone fear that their views would be seen as racist, sexist, or homophobic by 'Marxists'.
Again, the central, crucial abstract question (should anyone feel this alienated in the workplace?) and the difficult, complicated particular questions (why does this person, as an individual, feel so alienated, and are those feelings justified; do they reflect a work environment that unknowingly makes rigid ideological demands; do they reflect mental health issues; could this person comfortably work with a black/gay/female co-worker [which of these] without 'wearing a mask'; would a black/gay/female co-worker be able to work with them; would the situation be altered by empathy training, counselling, mediation; and so on...) These go unanswered.
And this is your response to someone's actual personal suffering, so one must infer that you do not oppose discrimination because it causes human suffering. If there is a different, justifiable basis for opposing discrimination, then you should be straightforwards about that, as this would be the most crucial aspect of your response by far.
[1] An oscillatory model of discriminatory impulses resulting in the balanced distribution of prejudice floats into my mind when I say this.