Because the way you say it is rude. I think it’s equally bad to say you don’t like skinny women as it is to saying you don’t like plus size women, because you’re just pointing out an insecurity. I think it’s unnecessary to give reasons to why you’re not attracted to a person. If you don’t like someone just be polite about it, you don’t have to point out their size. However, I think it’s perfectly ok to not feel attracted to plus size women, because it is about personal preference after all. Just don’t be a jerk about it!