I know this is an old thread.
And there is no need to add more arguments over those already exposed here.
However, in my opinion a rule made to discriminate because of your appearance either in RL or SL is a pure and simple violation of a fundamental human right.
Nevertheless, I think if a sim´s owner dont like a type of avatar in particular, should have at least the common sense to say so in the Second Life Search´s info note.
This way I will know in which places I am welcome or not. And save to me and to the affected group of people, the humiliation of being asked to leave.