Fighting a much bigger person?

Ignore him the best you can. As soon as you fight, you already lost because you have reduced yourself into his level. Do NOT worry about the size of your foe(if it comes down to a physical confrontation). Thanks to movies and television people have been conditioned to believe that a bigger person is guaranteed victory in any cirstance. Keep in mind, it's not the size of the dog in the fight, it's the size of the fight in the dog.