Matthew,
I agree on the bigotry. I don't see how it is wrong to be more eccentric and creatively engaged. Both organizations that David belongs to are vocal on their stance that to retain membership, a member must obey the laws of their country and behave in a socially responsible manner. As far as it seems, the "vampire" mythos is a metaphor used in its positive for personal growth; "Satan" is a symbol of rebellion against rigid and totalistic thought structures. Here's a short piece from the leader of the Church of Satan:
"Satan is a model or a mode of behavior. Satan in Hebrew means adversary or opposer; one who questions. Since we generally are skeptical atheists, we question all spirituality. We believe that carnality is all that exists and the spiritual dimensions are fictional. So we stand against eastern and western religions that promote fictions, according to our perspectives. So we are adversaries. Satan to us is an exemplar. When we look at how he is portrayed by Mark Twain in Letters from the Earth, or Byron, or Miltons Paradise Lost, he ends up being an inspirational symbol to us. We say we would like to be more like that. We will not bow our heads; we will be independent. We will constantly question." -
http://en.wikinews.org/wiki/Satanism:_An_interview_with_Church_of_Satan_High_Priest_Peter_Gilmore
I have also yet to see David's accusers provide reliable evidence that he is engaging in unlawful affairs (the actual "meat" of the issue). If so, it would also seem to put his membership in those organizations in jeopardy. It is more likely that it is a cheap shot to discredit him, mostly by a former friend.
PR is still a real concern (though asking David to not take a leadership role isn't necessary due to any dodgy aspects of his character).