Romney has been out in front against Gay marriage in an overwhelmingly liberal state. He actively opposed gay Marriage, writing an op ed in the WSJ and testifying before Congress against gay Marriage.
He is not "socially liberal"
He seems like a good man to me and clearly he's a great CEO and exceptionally bright, but he appears to be making a mistake here by saying he was never pro-choice when instead he should say that he changed his mind, and explain why.
When he ran for office against kennedy he was pro choice, pro gay rights(wanted to be a leader on this issue, even moreso than kennedy), pro aff action, pro civil unions, pro quotas in the work place, pro gun control. On top of that he urinated on national republicans, the contract with america, reagan and bush.