It doesn't really happen anymore, but when it does, I usually just don't bother responding, or just say something like "Whatever." and move on.
I think it's just better that way. Who cares what others think? If I like it, I like it. Simple as that. So, it's a kinda childish, but so are certain other things people do and say. No matter how old you get, you'll be doing something childish. I play games like Pokemon among other things. Nothing wrong with that at all. If you look down on someone for playing a children's game, you're just being a child yourself.