I'm reminded of something a wise man once told me (HNified a bit):
In every pairwise conversation there are 6 people:
1. Alice
2. Bob
3. Who Alice thinks she is.
4. Who Bob thinks he is.
5. Who Bob thinks Alice is
6. Who Alice things Bob is.
Perception plays an absurdly large part in communication, as do nonverbal cues. Frequently we adjust our message based on feedback we get from the listener. Those lacking "social graces" or communicating in just text on the internet don't get these cues, so the message comes out "harsher".
Complicating this, there is a lot of baggage each person attaches to words, phrases and general styles of questioning/commenting. So one person's harsh may be another's "in to it".
One example of all this I have experienced:
One time at a vendor show, me and some colleagues were in a small demo, presented by a sales guy and a few engineers from the company. During the Q&A, I started questioning the engineer pretty intensely with questions like:
Does it do $X? Why not? Do you plan on adding it?
(These are actually pretty neutral questions)
Then about another aspect I was really into some possibilities of:
Can I use it for $Y? Can I make $Y happen by this? What happens if I do $Z? How about if I work around that limitation like this and get $Y + $Z effectively?
(these are not neutral questions, they are me geeking out)
So after the demo some people thought I broke the engineer and ripped him a new one with the second set of questions, because I was rapid fire asking questions towards a goal. One engineer thought it was a fun "play with an idea time". The other engineer thought I was severely criticizing his work.
The sales guy and several of the audience members thought I was being unduly harsh by asking about the feature $X. Apparently this was a contentious issue that I knew nothing about. The engineers and others thought nothing of those questions.
Similarly: I frequently get frustrated when people wrap up valid criticism in fake nice BS. I don't want to hear "great thing, what if instead you did this". I really would rather just hear "What about this other method? Why not use that?" or even "Dude, 10s of googling would have shown you the flaws in that". Because an honest self assessment includes the fact that I don't know everything, and that many (most) of the things I come up with have also been thought of by other people, who may have found flaws in that reasoning.
I guess my point is there is a lot more than just "nerds are mean to each other" going on.