I think banning them would make them more popular, no?
You could think that, but would you be right? If Jobbik had been been banned in the outset, would the current Hungarian political scene be so noxious?Yes or it would be worse with the precedence of banning parties having been created.
I too is uncomfortable with the idea that people in parliament having difference opinion than me, but the problem with banning people with non-mainstream political view is that you never know when it's your views who's seen as outside the mainstream, and there's no better way to deal with views you disagree with than engage in discussion with them.
Of course I think if it can be proven that a party engage in violence (like Golden Dawn does) they should be banned, but no one should be banned for just being horrible people.