There are numerous Internet filter programs available, mainly to combat pornography but some do include music censorship utilities, which have varying degrees of success. I suppose it depends which file format the software is looking to block which determines what actually gets through.Media files come in many formats.
As a father and a musician I've never felt the need to censor any of the music my kids download.
They probably here and see a lot worse at school whether we as parents like it or not. My children quickly learnt how to sort "the grain from the chaff" anyway.
(Sorry not a lecture just a point view)