While I understand why the Swiss are tense about Muslim immigration/assimilation, I think banning minarets isn't going to help. Extremists in Switzerland are going to hold extremist views no matter how many minarets there are, so all this does is insult and possibly anger reasonable or moderate people who aren't causing any trouble.
I think in any society you're going to have extremist nutbags who hate other people. As long as they keep their nuttiness to themselves, leave them alone and they'll marginalize themselves. If they cause trouble for other people, apply the appropriate laws against incitement or assault and hold them accountable for their actions.