How can I stand up for myself without seeming rude or insecure?

I get a lot of rude comments on the way I look. I don't think that many people have actually flat-out called me ugly, but I do get a lot of people insulting my looks fairly often, calling my appearance weird, or telling me that my appearance makes them  "feel uncomfortable" or "freaks them out". It's really quite hurtful. How should I go about standing up for myself? I don't want to seem insecure and make myself even more of a target but I also don't want to seem too rude and be even more hated. Help!!