I do know the rules, and even quoted you the Blues confirming that the filter does not allow swearing.
You were told why the filter exists - and it is not to let you break the rules.
Feel free to directly go ask Blizzard on the CS forum if you want it in Blue. Here is a fairly recent post confirming exactly what I said.
Mostly, the mature language filter is not intended to give someone permission to use language that would otherwise be considered against our policies. It serves as a temporary shield, to help parents of minors and others, who do not wish to see such language, to block it.