Actually - in some instances, yes they have been or if they've been represented they're represented far more narrowly than they should be - particularly when casting actors who "look" Jewish in many types of roles. Ethnicity is one thing when it's apparent on the surface. But this is the natural extension of the complaints about actors playing roles of who they are not in real life. If you're going to complain about a straight actor playing a LGBT role or other roles where you now have to inquire with the actor things about them that aren't physically apparent, then this complaint is absolutely justified. I personally am not offended and don't mind the casting but to me it's a package deal with many of the other complaints I also don't agree with.