You would probably also suggest that if a woman keeps her legs closed she can't be raped? How quaint. This is clearly a disingenuous question from a man.

The ability to keep the mouth closed, or the legs together, relies on having superior strength to withstand the assault. If you're lucky and can fight back effectively, e.g. jab, kick, gouge, or bite, you can get away, but in this instance if she tried to say anything to protest (or breathe) she ended up with his cock in her mouth.

You're being willfully stupid to suggest that it is a simple matter to avoid this, let alone fight it off. Or bite it off. It just doesn't work that way.