Hey, we all have our opinions however, I disagree with your general tone towards grunge. I am not in any way into the genre grunge, but I can see why people would be into "pessimistic" or "depressing" music, as I grew up listening to KoRn which is very depressing music.
Just because you don't like a certain style of music, because there is enough depressing things in life, doesn't mean others will have the same outlook. Me for example, listening to "sad" music was a way to make me feel, and connect with another human on a level I was not getting from anywhere else.
Each style of music is going to make someone feel something different, whether it be positive or bad is subjective towards that individual person. I'm not asking everyone to start listening to genre's they dislike, but I don't see the need to make fun of or "hate" genre's when obviously there is something about those genres that people connect to and make them feel something.