it wasn't a fine moment but bans for simulation are given when there was absolutely no contact and the player simulates the contact altogether.
In Boateng's case, there was contact, even if he didn't exactly get his legs broken by it, and he more embellished it than fake it entirely. This would make a ban highly unlikely and would be probably overturned if given, at all.
again, not one of the finest moments for Milan fans, and they seem to agree on that with a vast majority.