There's a distinction between "shitposting" (or smack/trash talk) and actual hate speech. The lines can be blurry and I think Poe's law can lead to miscommunication in both directions, e.g.
* person A might say something outlandishly racist thinking it's obvious they can't be serious
* but person B actually thinks that's something perfectly reasonably to say and agrees
* which person A in turn misunderstands to mean person B is in on the joke
* 30 minutes later person A is wearing a Klansman hood in front of a burning cross and wondering how they ended up in that situation as it dawns on them they're surrounded by actual racists
I think this is how a lot of Internet trolls felt after the US elections. Some trolls just wanted to see the world burn (so Trump is the gift that keeps on giving) but many simply didn't think Trump could win (because surely people would just go for the unlikeable but safe establishment candidate rather than the obviously outrageous joke candidate).
The problem with maintaining that distinction in the digital age however is that it's very hard to tell apart the satire from the real thing. The joke works because the audience is in on it (e.g. rape jokes work because the audience and the joke teller have a mutual understanding that rape is horrible and joking about it is inappropriate -- the inappropriateness is what makes it funny) but the Internet is not the social equivalent of two friends talking smack in a pub or a comedian talking on stage in a comedy club, it's the equivalent of random people writing on a public wall or shouting in a massive crowd of strangers.
When talking to friends there's a mutual understanding of what is or isn't appropriate. There are numerous social cues that can indicate something deadpan is still meant as a joke. Even an actual misunderstanding may still come around as a funny story.
In a comedy club the environment sets the expectation. If the guy on stage calls to arms and rallies the crowd to overthrow the government the context makes it clear this isn't a serious attempt at rebellion but more likely a build up to some kind of punchline.
But on the Internet all that context is lost. Even a conversation between friends can still likely viewed by thousands or millions of other people, so the words stand on their own.
It's obviously still important to have these private exchanges but it's also obviously not appropriate to have them in public spaces where every passer-by might become a participant.