Somebody got to him. There is nothing new about the gay marriage argument. Suddenly he believes that its all about being “fair.” Well that argument was an obvious one when he championed prop 8. It may be that someone threatened to release the skeletons in his closet.
He was probably tired of becoming a hate figure for the Left. Supporters of same-sex marriage are vicious and spew venom on anyone who dares to stand up for traditional marriage. (Ironic that they love to accuse anyone who opposes SSM of “hate.”)
I think in the end Blankenhorn just found it too hard to put up with that kind of constant obloquy.