Depends, if i had a disruptive person in my platform then it is okay to ban them. Here, disruptive person means "Physically attacks other people or tried to rape someone", while these transgressions in particular are not the point in on itself but examples of unacceptable behavior that people from all the sides of the political or ideológical spectrum find or should find unacceptable.
Claiming that monarchy is the only acceptable form of government, that individual rights are the root of all evil, that we should take the possessions of other people away when they have too much, that any knid of statism is the devil, that everyone who is not satisfied with the current situation should shut up and pretend everything is fine because i want to grill. Those are all views i disagree with and can't imagine an argument where they would work but i would not consider them banneable offenses in a forum of discussion.
Denying the holocaust would be because that is something no side should find acceptable.