Supporting violence and hate isn't acceptable in any other format, why should the Internet be excluded.
Furthermore, while "hate" speech is not the best use of our ability to communicate it does fall under the protection of free speech - at least in the United States. In some groups hate speech (however it is you describe it) is acceptable.
Just as you are free to not associate with those groups the internet should be free to express the ideas you disagree with.
You don't have the freedom to interfere or disrupt the freedoms of others.
The west has enemies and stirs up hate and uses violence to target them, adding to the mayhem in the middle east, killing 10s of thousands of people every year.
Violence is very acceptable for the western democracies. You have to be willfully ignorant not to see this, after the last two years and 70000 people killed by the coalition during that time.
How so? I don't see it.
edit: Anyway. There's a lot of hate towards real or believed enemies of the west. It's easily visible online in news websites' comment sections, on social media, etc. It is somewhat rare to see people standing up against it. Even on platforms, where you need to provide gov. ID to be able to discuss, and your name is visible to others, people feel perfectly fine to spew hate against muslims, ISIS, or whatever in very non-measured ways.
My point with the previous comment is, that it is important to realize the western hate and violence too and not to brush it away, because it's very significant in its effect on peoples lives.
I'm not from the US, so it might be different in different countries.
However we have recently seen that principle degrade with all kinds of exceptions. It's weird given how little potential islamist terrorism has in the west compared to what communism, republicanism or protestantism had in the past.