Forcing/pressuring someone to top or be dominant for you during sex is sexual abuse.
Yes, even if that person identifies as a man.
Yes, even if that person is usually masculine.
Yes, even if you're queer and it's a queer relationship.
Especially if that person has a body that gets stereotyped as automatically masculine or dominant, such as fat, tall, or muscular people. I don't care if fandoms make you believe that bigness equates to a specific sexual position.
Especially if that person said yes because they felt pressured to please you or to follow the gender/body norms put on them. Consent is not an "I guess." You need to give a person the safety to say no.
Especially if you are misgendering that person, including a cis person. Pressuring a fat cis woman to masquerade as a man for you in bed is not okay because pressure is not consent.
Sexual abuse is not just faced by a person who is penetrated, is submissive, is smaller, is a woman, or whatever other stereotypes society pretends are requirements to count as sexual abuse. Sexual abuse isn't even just full on rape, and the sexual abuse that isn't full on rape is still able to create unbearable trauma that matters just as much, that affects a person mentally and physically for possibly the rest of their life if they are not given the support needed to recover.
And when a person has experienced sexual abuse but is not a woman, was not submissive, was not being penetrated, was not smaller than the other person(s), or did not experience sexual abuse that is viewed as full on rape, then it is that much harder for that person to receive the support and help they need.
How someone looks does not tell you what they are comfortable with sexually, and it sure doesn't tell you whether that person is capable of facing sexual abuse.