Why aren't men allowed to get raped?

So in a fair age of equality (another issue) aren't women allowed to rape men? Why are they protected? Why is it such a taboo to laugh at? It's disgusting and the one time I told a guy I would have raped him to his face if I had the chance he got VERY upset and told me I was a sick woman. I didn't even say it in a serious manner but he was mad. It's very weird.