Your position, although yours, to me, is quite extreme. Instead of taking an opportunity to possibly witness to them, you'd rather ostracize them. Cult or not, most are quite ignorant of what their doctrine actually involves.
Btw, you needn't worry about a mormon group seeking service in your pizza place on Sunday...they typically don't do anything but go to church, a few meetings and then hang at home...
It was just an example ... It can be Monday, Tuesday, Wednesday, Thursday, Friday or Saturday ... too! ... :-) ...
BUT ... what I consider EXTREME is Mormon teachings and doctrines sending a person STRAIGHT TO HELL for ETERNITY. Now, THAT is extreme!