Yeah it's just like a guy saying "all metal sucks". Most genres are simply too broad and too varied to dismiss (especially when you know little about them). Of course, you can dislike a genre, but can't you make a broad generalization and expect it to be received with any respect. I think it's better to have the stance "well I haven't heard anything from x genre that interests me yet, but I will keep an open mind" and so forth. Because more often than not in my experience, eventually you do find something that interests you.