Us blokes exaggerate size we do.
We would do measurements on the door at school. the lads would all ways stand on tiptoe till teacher shouted.
5'9" is pretty average for an American male, but so what? You are not responsible for your height. You are what you are, and you should accept it. You are fine.
That is not your problem. It is his. He was obviously insecure about something so he had to try to make you feel like he was better than you, somehow. A secure and happy person doesn't have to bring someone else down to feel good about himself. He probably had someone at home who told him he would never measure up to some ideal, so he had to pass on the misery.
The fact is there are a lot of things that are far more important about you than your height. You are taller then some guy who is only 5'6", and I'll bet he could also make you feel bad about yourself, by saying his IQ is 10 points higher than yours, or his blond hair is prettier than your brown hair. You have to find your own sense of security and believe that you are exactly what you are meant to be.