Because this is a game. A game is different than murder. Murder is a crime. Most of here, myself included are in their 30's and have children. I have a son that enjoys watching me play and plays also. But I will not play on a server that allows swearing, nor will I allow him to play. I also refain from swearing in front of him or allow others to swear in our presence.
Most people know the difference between a game and a crime.
These are our rules and we expect people to abide by them. If they do not like it or cannot refrain themselves to follow our rules, we gladly show them the door.