my mom always told me that if someone says something bad to you, don't retaliate aggressively. just say "ok" and don't really show any emotion. it works sometimes for me. if they're being particularly problematic, don't take it too personally. you probably can't cure their ignorance in a single visit, so try to keep that in mind for your own sanity. Also don't forget that you can always just go outside or go to the bathroom, and if they're bothering you a lot just "go for a nap" or hit the hay early.
good luck!