Liberals say that they are good, tolerant, kind, intelligent, moral, rational. This is branding, not reality, but the news media is biased left, so it reinforces this narrative.
This narrative means those that aren't liberal get labeled bad, intolerant, mean, stupid, irrational, haters.
The hate speech movement sounds good, "let's punish those who say kill X group", but the end result is "you posted conservative views, those views are based on hate, ban that speech and punish him for uttering it".
You get the same double standard in real life when Twitter even allows hateful hash tags like
but bans Milo Yianapolis for arguing with a black actress from Ghost Busters after a negative movie review and calls her a him, a woman who herself was unpunished for Tweets bashing all whites.
In such an environment, people should be afraid and angry that whole classes of ideas are being punished under the guise of protecting specific classes of people. We know it isn't out of respect of all people, or you wouldn't see hash tags like those above tolerated much less the calls for violence associated with them, or the #polarbearhunting and #KnockOutGame hash tags with videos of where blacks try to knock out whites with one blow to the head, not caring about the brain damage and death it causes.
When one side says "your criticism of illegal immigration undermining rule of law is racist, ban hate speech, you can't express your views anymore", you get the more extreme demagogues standing up because they are the only ones able to express the views more polite society still holds but can't express.
(Yes, SJWs, Donald Trump's rise is your fault for calling everyone who disagreed with you bad names and tried to get the more prominent ones fired, so they resort to the last person standing who says what they think.)
And everyone who is afraid of persecution for thought crimes ends up afraid of the state, for being punished for saying the wrong thing, or even more immorally, saying something that one demographic group can but their group isn't allowed to say.