I'm at the point now, and this is a process for me, where I'm trying to recognize that all forms of music are equally valid. This extends to other things too - food, movies, clothing styles etc...
I'm not an objective judge of anything, and therefore I don't think I should use words like "good" or "bad" music, the words that I try to use now are music that I "like" and "don't like". When somebody says, "this music sucks" or, "this music is stupid", what tends to happen is that if you're with a person who LIKES that music, is that they feel as if you're saying that they suck and/or are stupid. This is a great way to ruin a dialogue or a first impression.
Of course, try talking to a person with the aforementioned attitudes about this concept, and they'll invariably act like their opinion is just naturally objectively correct that X music sucks. This happens with everybody, and everything, the only thing I advise to do about it is to just walk away.