You're being ridiculous. These kinds of people exist. They exist in the real world and they exist online. The fact that they exist doesn't ruin anything for anyone. You just ignore them (unless they become actual threats) just like you do in real life. See: Westboro Baptist Church.

I think the most vitriolic reactions have been from non-community people.

Yes, the "activists" who insert themselves to disrupt other communities to promote their own personal infamy.

I hesitate to call a random teenager that reads reddit, 4chan and knows how to download LOIC an "activist", even with the quotes around it.

How do you "root" people out who are using random Twitter accounts to post garbage?

Good question. But as long as this happens, no sane discussion is possible via an online medium.