Ban them. Certainly for domestic games.
I recall a few seasons ago in the Summerbee Bar there were 2 Dippers who had obviously somehow got tickets in the home section. Otherwise they wouldn't have got entry into the bar. I only noticed them because of their accents and they were wearing half & half scarves and once they had bought a drink they both turned their scarves around and tied them with the red half clearly to the front. Asking for trouble.
The other thing I don't get is people wearing them at Derby games. I saw plenty last Sunday. No self respecting Blue ( or rag, for that matter) would wear the opponents' colours. They're an abomination and should be permitted for CL games only, at a push.