I feel like some of this may be more pronounced in areas like SV. Specifically, areas of the highest competition. The personality traits that correlate most strongly with success are: high conscientiousness, high stress tolerance, and low agreeableness. Of course it makes sense that the people in the areas of stiffest competition in tech are in an environment of high stress and are generally really disagreeable to be around. This is going to be the case at the top of any field with stiff competition.
I live in a 2nd tier city (not NY, SF, LA, etc) and these depictions of the "tech industry" are unfamiliar to me. Sure, there's the odd asshole, but those are everywhere. I feel like people around SV and other high competition big cities are generalizing about the industry in a way that doesn't reflect my day to day life.