I strongly suspect that the competitive environment in Javascript frameworks and :s/tool/fool/ing is the main source of the negativity:
Trolls have the explicit agenda to demolish/demotivate what they're trolling in order to push their own project/framework.
I have found that even sites like HN don't skew significantly far from this. As users, we can't know who the 90% of people are who read this site and never post. But there are definitely 9 times more people commenting than creating.
As an open source project maintainer myself, I have absolutely zero time to go talk shit about my competitors, even if I had shit to say about them.