"Who am I to say if it's wrong to believe people should be killed and enslaved for their skin color? Next thing you know, someone may think I'm extreme for what coffee I drink!"
Your argument is inane.
We wouldn't be having this conversation if the things labeled extremism and thus banned from platforms was limited to ISIS and literal Nazis. It's been far more far-reaching than that. That's probably due to the incentives, not due to actual extremism.
So if extremism is subjective, it will be leveraged in that manner and you can't stop that behavior without removing the incentive. That's the point, not what is or isn't labeled as extremism today, that's just dragging the conversation back into the political gutter.
I don't think that's the next step. I think the point is that what is extreme will always be subjective, and there is danger in allowing some group of people to decide what speech is acceptable and what is not.
That's true, but it also seems to effectively hold for the originals, only with conformity rather than contrarianism:
> Someone: Extremism is bad.
Someone: Extremism is bad.
You: What is extreme is subjective.
The next step would be for you to try to give counter points of what you think is extreme that others consider not, or better, what you think is not extreme that others consider so.