He obviously has some need to hurt other people to make himself feel better! Explain to him that you DO brush your teeth, and that you are "growing out" your hair until it's long enough for the style you really want.

Then tell him that he may think you are ugly (he's wrong, but that's not my point), but he was mean, and beauty is on the surface, but meanness goes straight to the core. There is nothing as ugly as a mean person, no matter their physical attributes.

There is nothing as beautiful as kindness.