It goes like this:
Why in blazes would anyone want to belong to a group which hates them?
The Bible is crystal clear that homosexuality is a capital crime. Why would a Gay person want to be a member of any religion which has that at its core?
The Republican Party is rooted firmly in those same teachings. Why would a Gay person want to be a member of that party?
I saw a posting on the Silicon Valley Atheists' message board asking for suggestions on people to officiate at an atheist wedding. Weddings are an artifact of religion - why would any atheist want a wedding ceremony?
Tangentially it all reminds me of that famous Grouch Marx quote, when he was invited to join an otherwise no-Jews-allowed country club, "I don't want to join any club which would accept me as a member"