No matter where you are, no matter who you're with, swearing is going to be present. I agree that younger children should not be exposed to this language, but from my own experiences, this would be the opposite. I cannot tell you how many times I've heard swearing language being used by kids in elementary or just entering middle school. To me, it's disturbing, but in another sense, it's natural. It's not always on the child, but the parent as well. More parents, most likely due to the growing advances in technology, do not know what their child is exposed to or the other children they surround themselves with.
I take into the consideration of those who are always subjected to offensive language and eventually caught onto it. In this case, there's not really anything to be done except the right people or alternative parenting to step in.
Now, with games, swearing is almost guaranteed. Any game, especially ones that are aimed for either younger audiences or the adolescent group, should have filters of certain words as stated by Kijiako. This would helpful in eliminating the amount of inappropriate language in a game. In addition, with inappropriate language, usually follows in inappropriate behavior as well. If a game allows one thing, more than likely, something else can come after.