If someone comes into a store, for example, then you can remove that person for harassing other customers because his purpose for being in the store is conducting transactions for the purchase of items.

However, Twitter isn't like that. It's a virtual public square, and may be considered a common carrier. It makes its money off the fact that people post opinions. While a common carrier or public square can regulate harassment or other abusive behavior directed at another user (spamming, doxxing, threats, etc.) it cannot discriminate simply because someone holds an opinion that the carrier finds offensive. That is policing opinion.

This used to be something that people didn't need explaining. When the ACLU went to court for the Nazis so they could march through Jewish Skokie, they hit the nail on the head with respect to the principle. If one of those marching Nazis had gone up to a house and said, "We're going to burn you alive, Jews", then it would be possible to prosecute that asshole for making threats or harassing someone.

Similarly, someone could post about how they hate a particular ethnic group and use an ethnic slur to describe that group, but replying to everything someone from that group writes with the racial slur would be harassment.

The standard changes slightly when someone becomes a public figure. In that case, parody and satire are generally protected so long as they do not rise to the level of harassment. Larry Flynt proved this with his infamous parody ad involving Jerry Falwell, which made it sound like Falwell fucked his mother in an outhouse as his "first time". The fact that the Babylon Bee was banned for a parody that points out an incontrovertible biological fact makes it even more reprehensible, as even in defamation cases the truth is an absolute defense.

I should be able to write article after article saying that the guy in question is a man deluded into believing he is a woman. If I go after him by replying to everything he writes with "You're a man! Wake the fuck up you fucking mental case" then I am engaging in harassment.

It's also worth noting that the so-called trans lobby is entirely about shutting people up and throwing little hissy fits when others don't comply. There's a word for the notion that you can shut up people who disagree with you. It starts with an "f" and rhymes with "fascism".

If Twitter stops policing viewpoints and limits its bans and deletions to threats of violence, harassment, posts with child pornography, doxxing, and the like, then it's a better place. If someone wants to try to convince me that a guy can become a girl, perhaps some logic would work better than trying to silence me on a social medium.