I will agree with you on the first part. Everyone has their own taste and if you want to bash the music then do it with people who will bash it with you, not the people who will be bashed.
But sometimes people with bad taste need to know it. Sure they like what they like and I like what I like, but if this person honestly believes that what they listen to is better than anything else then we have serious problems. If they brag about the band all the time like they are GOD then someone should tell them.
I think the music I listen to is awesome, and I don't like anything else, but I recognize the talent and the effort and everything else that is in the music. But sometimes I don't like the reasons, or the methods or the people or the lyrics or what they stand for or whatever, but I keep it to myself unless a fan of one of those bands comes around acting like they are more talented that the most talented musicians you can think of.