Because public discourse isn't a forum. Even within that example, GAF doesn't even collectively agree on what's a bannable action or not. The moderators themselves don't either. There's some absolutely heinous shit on here that slides right by because it comes from the right side of an argument. Or is used as a weapon against someone the mod team doesn't like. Or comes from someone the mod team does like. When you begin to assume that the collective, or society, has decided something isn't worthy, you begin projecting your own opinions and confirmation biases.
The other issue is that you can't control all of public discourse like you can a private forum. The situation wouldn't be banning someone from the forum because they are troll; you'd be banning them from specific threads - but still allowing them to post in every other thread on the forum. You aren't removing them, you are disengaging from them - which is entirely different and where the actual problem lies.
Donald Trump was elected President after saying a dozen things a day that would have torpedoed anyone else's entire political career permanently. Obviously what you and I may believe to be unacceptable public discourse clearly isn't.
So trying to filter out the noise through disengagement isn't going to work. It doesn't work. It hasn't been working.
The war on ideology isn't won by shutting out the other side and hoping they get ignored, as much as we'd all love that to happen. It happens by dragging these idiots out of the corners they comfortably spout their bullshit from and convincing people to join your side. Not everyone is going to be convinced, sure. Hell, most people won't. But that shouldn't preclude you from even trying.
That's why we have shitshows like Bill Nye debating Ken Hamm over evolution. Everyone with a elementary understanding of science knows Hamm is utterly and completely full of shit, so why bother engaging him and his bullshit? Because a fucking crazy amount of people still either believe him, don't understand, don't care, or simply don't know. You do it because, when liberals present their arguments in a reasonable, professional manner, we always gain social traction. Maybe we only inform or convert 0.1%. But that's still 0.1% more than before.
But for some dumb reason, we are so fucking scared that 'giving them a platform', even though they already have several, will mean that people will join the wrong side and we'll lose traction, despite this almost never being the case. Nearly everytime we go head-to-head with staunch conservatives, we gain a little bit. That's why you do it. Not because it's the right thing to do, or the fair thing to do, or whatever other nonsense conservatives cook up for allowing hate speech. But because it fucking works.
Yeah, sure, there's always a bunch of people on the other side that will claim victory, or double down, or whatever. But those people will always exist and everyone needs to stop focusing on them. We're not moving the needle by absolutes. We're moving it by fractions of a percent. And no one has ever been convinced by continually screaming "You're fucking wrong" at them.
Very well said.