I'm more bothered by the heteronormativity and rigidness that is often portrayed in the relationships. Some people like one or the other, but there's so few series that explore the possibility of liking both.
But yes, the "bottom" characters are often depicted as physically and mentally timid and weak. Or they suddenly become that when another dude starts hitting on them and they reciprocate. It's annoying.
See, Drew, you got me ranting. Good job.