When someone is being especially obnoxious about something I enjoy, I smile sweetly and say, " Well opinions are like {impolite term for where you go to the bathroom from} everyone has one, but you don't need to share."
That shuts them up 99 times out of 100. For the remaining 1? You simply shrug and say, "Well, not everyone has something they are compensating for, so I'll stick to my {whatever it is they are badmouthing.}"
Gale