I certainly am not put off by Santorum’s answer but leftist interviewers are well versed in crafting questions where any answer can be spun into something negative. Thus the most correct path is to attack the very premise of the question, and do it in a way which allows you to bring the conversation back to the failings of statism.
Cruz's reply was fine.
I also support anyone who attacks the canard that there can be a marriage between anyone but one man and one woman. I don't know if Santorum said anything other than 'no' - but it would have been good to have launched into the reasons 'why'. Namely - we may love the people involved, but we are not going to celebrate their spiritual suicide. It would be analogous to a friend, or relative, inviting me to watch them slice their arms up with a knife, or to shoot up drugs. If I can't stop them - I certainly am not going to be party to their self-destruction.
Sure, Santorum would've been thereafter branded an unelectable kook - but at least he might get some people thinking about what is at stake here. He's not going to be elected anyways. The Conservatives will gravitate to Cruz and Walker and the big government RINOs to Bush and Christie. I suppose Santorum, Fiorina, and the others will hang around - but I don't see them capturing much of the vote.