Vegetarian-What should I do?

My parents are divorced.. When I was with my dad the other day I jokingly said to him (just to see what his reaction was) "Well maybe I'm a vegetarian". He laughed and said, "Tay, you can be anything you want to be EXCEPT a vegetarian." 2 days later I told my mom what he said (in the same jokingly way), and she told me that she "has to agree with" my dad. I'm against torturing, killing, and eating animals, but I don't know how to tell my parents this. Help?