A lot of the time it is also just lack of understanding of how others will respond.
A lot of "nerd bullying" is unintended and seem to happen through brutally harsh technical criticism that we often don't realize can affect others really badly.
I used to work with a now well known blogger who is reasonably technical, but not a developer, and I used to fall prey to this with him.
In one meeting, we were chatting while waiting for someone to bring some documents, and he told me "when I first met you, I thought you were a total jerk, because it seemed like in every meeting when I opened my mouth, you'd shoot me down". After a while he realised it wasn't personal, but he still didn't quite understand why I was seemingly picking on him.
And it was true. I did shoot him down a lot. But I was flabbergasted. To me, my criticism was essential technical discussion. What's more, as I told him, the only reason I often criticised his ideas was because they were often good. Good ideas deserve thorough attention. Good ideas deserve criticism, because it is by fixing the rough edges we turn a good idea into something great. I had, and have, a huge amount of respect for his ideas.
The reason I kept my mouth shut when a lot of the rest of the management team came up with suggestions was because I often didn't believe they were interesting enough to be worth it, and I had a good idea for when any of those ideas might get traction enough to be worth shooting down, but mostly the bad ideas just got me to pull back and think about something else.
Sometimes we do bring out the heavy guns for really bad ideas too, but even then there is often a tacit admission of respect on some level, though influence rather than technical proficiency: Only the really insecure or clueless wastes lots of time criticising someone with no influence. We criticise bad ideas incredibly harshly when they come from people who have the influence to push their ideas through regardless.
But that is rarely aimed at someone who would be all that phased. And at least in my environment, the less technical members of the team would often easily recognise and kill those bad ideas without any need for me to pick them apart. More often for me at least, it was people I respected with ideas I respected that got the tough responses, because they got my attention.
Back then, I didn't understand that this kind of harsh language was not taken as impersonal technical discussion aimed at helping to improve their ideas by "normal" people, but as intense personal criticism.
I hope I've improved in that respect, but I still far too often cringe at when I see my "old self" reflected in overly harsh responses that still seem to be well intended.