This is exactly what free speech is. The freedom to say things that are wrong, hateful, misinformed, misleading, vicious, cruel and hurtful as long as no actual violent or criminal acts are incited.
Having ten thousand people on twitter continually tweet at one person, or email them, or whatever, is kind of like a psychic DDoS. This is a thorny problem for freedom-of-speech absolutists who can recognize the harms such things may allow.
However, shitty subreddits? There's nothing there to offend anyone until they go to the subreddit and become offended. People in those cases are basically autoharassing themselves.
It's just so shitty to see a few crybabies and a few shitheads drum up enough drama to cause everyone to forget just how awesome it is that we had this nice, open platform for idea exchange--even the ones the majority dislikes.
EDIT:
And lest we forget, the newsgroups and BBSs and everything were more than happy to allow people with nonstandard gender configurations and sexual tastes to merrily congregate, as they did other weird and sometimes hostile subcultures.
That people want to remove the facilities to support such formations, now that $PREFERRED_CULTURE is mainstream enough, is pretty harmful.
Fatpeoplehate would often brigade other subs and other sites.
"These people we don't like used this coffeeshop to organize their protests. Therefore, let's shut down this coffeeshop."