What to do about my best mate taking the piss out off my dad?

Ok so basically, when my and my mate were walking home from school, he was talking about how when he got on a 236 bus and the bus driver started "bitching" about his oyster card and he told him to **** of and described how he looked like. And it was my ******* DAD (He drives a 236 bus). but i didnt tell him but when i got home i whanted to just beat the **** out of him but hes my best mate and the only one worth talking too, Help?