It's possible he wants to ban blowjobs. Especially if it's dude on dude. I doubt it's the case he wants to ban them for everybody.
His point in the above quote is to make a sort of slippery slope argument from Lawrence v. Texas and thereby argue against the straw man of "you have the constitutional right to 'anything goes' in the bedroom as long as its consensual".
It seems like he's saying the "you have a right to 'anything goes'" idea is what would "undermine the fabric of our society" because it logically (to Santorum) leads to all sorts of things (incest, bigamy, etc.) becoming legal.
His goal is to support the idea that <i>in general</i> the govt. needs to be able to dictate what you can and can't do in your bedroom, not necessarily to argue that gay sex should stay illegal. He may <i>also</i> think gay sex should stay illegal, but I'm not sure you can positively conclude that from this quote.
I kind of wish someone would just ask him in an interview. "Do you believe the constitution allows for a state to pass legislation prohibiting private, consensual, homosexual sex between consenting non-related adults?" Followed by, "If there were a referendum in your state about whether to enact such a prohibition, would you support its enactment or not?"
Then we'd know for sure.