ok from our chat online I can tell you have three options.
1. prove you are mature enough to use a computer without parental filters
2. find a series of parental filters your dad can use that won't interfere with AIM or .Mac
3. If you really want to block some one who is bothering you then have your dad log in under an account that does not have any parental controls and block those people for you.
forget number 3, I never really need to block people, but I noticed it, so I'm bothered that I cannot block anyone. 2, My dad thinks apple is the best at everything, so giving him an alternative the apple is already doing...he'll just say apple is better.
number 1, I have written 10+ long emails about it, he just ignores it, I guess he thinks I'm some kind of perve....