Why do men have to respect females....?

Why do men have to respect females when they turn around and treat you like trash in return. From a very young age I was taught to treat women right and respect them and cherish them. What I didn't learn is how they treat you like common trash in return. I'm sick and tired of breaking my back to be a gentleman and getting spat on as a reward. So I ask why should men respect women when they don't return the favor?