You either respect their wishes or you do it in secret, which should you do? no one here can give you the answer Im affraid. By the sounds of things your very young, couldnt you make a compromise and ask if you can just do the non contact aspects? at least then when the time comes that you dont need your parents blessing you will be in good shape and ready to rock and roll.

You did tell them that you are more likely to get hurt playing golf than you are boxing right?

Good luck