That comment/subdiscussion you're linking to on the subreddit seems like a pretty good examination of the relationship that's developed between him and the alt-right. Or at least part of one.
But I'm puzzled by the statement that the comment you're responding to accurately describes Peterson's views on race. Except maybe in narrow categories that don't match up particularly well with a broad conception like "race" (e.g., Ashkenazi Jews), I can't recall any instances of him asserting a correlation between race and IQ, though it's possible I've missed something, and I'm open to visiting anything you might want to point out.
And I also think that it's a mistake to boil the alt-right relationship down to race issues. I think it starts elsewhere. In addition to the points in that reddit discussion, I think there's a fundamental shared narrative that goes something like this:
"Some (or all!) of the people and institutions that make up society are hostile to people speaking the truth freely. Maybe even more hostile to it than they were in the past. They are hostile to it because they are weak and corrupt and tyrannical. But it's important thing for people to speak up anyway."
Peterson absolutely says this, repeatedly and quite clearly. And it resonates, because most people probably have been in situations where they've faced hostility and even retaliation for saying something that others didn't like.
And I think if you pressed Peterson, he would probably say that this narrative is part of the human condition, and the reason why he frames the problem as people being weak and corrupt and tyrannical is that it's a known failure mode for pretty much all of humanity and it's probably true in some degree inside every single human being. And it's important to speak up anyway not necessarily because you are the sole promethean bearer of The Truth, but because nobody is the lone possessor of the truth and we will likely do better at working things out if we have conversations and negotiate. I think this line of argument has some limits that I'm not sure are sufficiently explored, but it's a pretty compelling one based on my own introspection and observation of humans, though I also find that the degree of "corrupt"ness in the hypothetical human you're dealing with matters a lot, and I also think Peterson may underestimate the downside of using language like "weak and corrupt and tyrannical" because it invites contempt into the understanding of the situation and that usually doesn't make things better.
But for some segments of the right (among other people), I think this narrative often goes farther. It is not a description of part of what it's like to exist as a human among other humans, it is part of repeated liturgy about the problem of being a conservative in a society besieged by malevolent political opposition. It says that conservatives in particular are unjustly singled out for this kind of treatment, and that it's much more often because of bias rather than any flaws in their own position, and that the weak and corrupt and tyrannical people are Marxists who want a totalitarian state, and what you have to say is not only important because the process of dialogue helps with synthesis but it's important because it's the Capital-RT Real Truth whose only flaw is that too many people aren't brave or strong enough to look it in the eye and understand it, and the only hope is that you repeat it often and strongly enough without being seduced.
(And again, the right is hardly the only segment of humanity that starts to think like this, but I don't think there's any credible argument that this narrative isn't deeply embedded in current political conservatism in the US.)
Now, I happen to think that there's an important distinction between the former and the latter formation of this narrative. But no matter how nuanced someone is being, if you lower the resolution at which you're listening to someone present both, you might not be able to tell the difference. One could imagine that someone who can't tell the difference between "IQ matters and has a genetic component" and "you can make sensible generalizations about a person's IQ by race (and we should!)" might have precisely that problem.
And though I think JBP tends to be nuanced and I try to pay attention to that... frankly, there are times when I can't tell the difference between the former and the latter (which seems weird to me considering how widely prevalent and accepted many conservative ideas among my social circle and in the institutions I tend to participate in. But then again, I don't work at a University, and I grew up in a conservative state and am part of a religious subculture, and so most of the time when I'm facing an uphill battle in a discussion it's quite the opposite).
So I think that's where the love-in begins. It probably also helps that JBP defends the value and message of traditional religious stories and focuses quite a bit on personal responsibility (perhaps as contrasted with state measures) and the merits of conscientiousness and bringing order into the world -- all things that are likely to resonate with conservatives.