One that always drives me crazy and I see in a lot of circles is "_______ isn't real art." Like people who will say you're not really making art because you work in a digital medium or you don't draw original characters. Like, art is art. It's so narrow minded and it annoys me because they're just not acknowledging the fact that someone put real work into it.
That one particularly irks me, it's like they're trying to justify their artistic preference as if it's something objective like science or mathematics.
But art... isn't really objective in that sense. How you feel about art, whether it's visual or musical is completely and totally subjective, and there's no need to justify why you feel that way. What's wrong with saying something just wasn't your thing? That's completely okay.
Like, in the Anime OP/ED thread, the pieces I rated were 100% based on how I felt about them, not necessarily that they were bad art in an objective sense, because they aren't. In fact, they were good pieces, I just have my opinions as do we all.
But my opinions aren't objective fact. It's just my personal feeling about them, and that's totally fine.