The problem is that this new policy is like Twitter saying nudity on their property will be prosecuted. Twitter then leaves their property, goes to the house of some guy they hate, peeks over their fence to see them sunbathing nude, then Twitter goes back to their property and calls the cops to report the person sunbathing nude on their front lawn.
It's not quite like that, in that that's a legal issue and this is not. If it were a legal issue like getting arrested for public nudity, you have consitutitonal rights. You don't have consitutional rights when using a private website (which is why it's exceptional when people say a website is restricting their right to free speech), so it's completely within their rights to ban you for whatever they feel like, and you're not in a position to dispute it.
Of course, the issue with a website abusing that condition is that if they want people to leave their website, they will. When you're a business like Twitter, your users are your customers, and you have to think long and hard about when you tell one to stop giving you money.