Its not about how big you are. It's how good you are at holding others down.
Is this meant to be a joke about rape? I don't think that's appropriate.
It's just a joke. I don't see how a joke can be hurtful or harmful.
Although you are just joking, when people make light of rape or sexual assault, it makes it more difficult for victims to come forward. When jokes about rape are normalized, people feel like they won't be believed if they come forward about their experiences. It would be best to tell family friendly jokes instead of ones at the expense of victims of sexual assault.