My freedom of expression is limited in two ways: First, it is wrong for me to pass off someone else's work as my own or to incite violence or discrimination. Secondly, if I say something boring or stupid few people will listen.
Banning people or their work only undermines this second, natural, limitation and makes everything interesting, no matter what its merits.
Banning Wilders is profoundly stupid. It is more likely to polarise and inflame than calm things down.