The game is rated M for mature. The multiplayer is unrated.
Would I let my kid play it? Yes.
Would I be upset if he asked me what the dick was on someone's emblem? Yes.
But then as a parent, you explain to them.
It's pretty funny because most of the kids that play the game are the ones with innappropiate emblems. The kids think it's funny to make and show their friends over PSN and they all laugh about how "funny" it is.