What's the Word on Yo Momma Jokes?

So my son seems to be the master of "Yo Momma" jokes lately.  I don't know what to think of this.  Sure, from a political correctness standpoint they are awful.  But, what about from a right of passage stand point? A way to have some fun with friends? I'm sure Chris Rock told Yo Momma jokes, heck he is part of one - "Yo Momma's so stupid she thinks Chris Rock is a new type of crack."  Is this offensive to you? He is not trying to hurt people's feelings, he and his friends just get to dueling with them with each other.  The other day he told us, "Yo Mama's so fat when she saw a school bus full of white kids, she hollered Twinkie."  The whole family busted up.  What do you  think? Should I place a ban on Yo' Mama jokes or just let them ride until he moves on?