I hate when all these "rules" magically appear! No where that I know is it written that we can not associate with certain fraternities.
When Phi Delt's got in trouble on our campus they lost social privilages for a year, so we were told that we shouldn't have any events with them until that was over. But I have never been told to never associate with any specific frats or organizations. If you don't comply... what happens, and what happened with this frat that our nationals would know?
The only reason I could think of is that they are on a different campus/college.