Some cults do walk a fine line between what the 1st Amendment allows and crime.

Over here, legislation is a tad harsher than in the US about cults. See this law and the American reaction to it.

C'THULU WILL RISE BEWARE THE SLIME FROM DEEP BELOW THE WAVES

I agree with you completely that cults are bad, and should not be allowed to stay around, but changing something like an amendment can be very difficult like you said. As nice as it would be to get rid of most of them(or at least the really bad ones), it is probably never going to happen, they will always find a way to get the followers they want. =(

You don't want to go down this road. If they can ban a "cult", the next thing they can ban is a lifestyle, maybe even yours. I think we have to take the bad with the good, in this case.

+1100 to what Mark said.

People have to be allowed to be stupid, right up to the point where it becomes a crime.

The way to eliminate cults is to improve the lves of people and make them strong so they don't need to cling to them. Still not an easy answer huh?