US law states that speech like doxxing are not free speech thus restricting it is not censorship.
"Without limiting the generality of the foregoing, User Contributions must NOT: Be obscene, sexually explicit or pornographic."
A law can be added to protect this right like the right to be forgotten. We didn't think the right to be forgotten was even a right that is valuable to protect but here we are.
Twitter and other social media are moderated in several ways. If your opinion is unpopular, it'll likely not be retweeted much, it may be moderated down by users and moderators, your account might even be banned. Private platforms are private, and regulating them would hinder freedoms to create and maintain diversity of such platforms in the future, ie. hinder competing platforms and innovation.
If such platforms become detrimental to society, that of course need to be addressed in some way. Right to be forgotten is a good example trying to balance out some of the imbalances.
You have your freedom to enjoy nude in your home but not in theaters due to city regulations. That doesn't mean that the city is censoring.
Similarly we don't call stopping robbery and murder censorship of our acts.
Gab is not censorship free. They've banned users.
https://twitter.com/willsommer/status/981984571645362176