Wash that mouth out girl!

Yesterday, while at the YMCA a girl told my son to go to f*****g h**l. Why? Because he didn't want to listen to her gush on about her life and when she told him something he said "whatever". I'll tell you - if someone ever hears any of my children swear, I pray they tell me. It will not be a good day (or month) for my child if I ever hear about it.
I bet the mother of this girl has no clue her 12 year old daughter is talking that way.
I so wanted to call the Y director and complain (the counselor who my son told did nothing). But, I can't "come to his rescue" all the time. He's got to learn to handle difficult people and situations. We discussed how perhaps he could have been more polite to the girl from the beginning, and how you should be courteous even to annoying people . . . .
Man, parenting older kids is less physically draining (I'm not running around playing with him all the time, he cleans up his own toys and can change his own clothes) - but it's tough in a whole 'nother way!