This is a complete straw man. 'Barging into people's bedrooms' is forbidden by the fourth amendment. if you're going to argue against Santorum, do it honestly.
You're missing the point.
If barging into people's bedrooms is forbidden, then the entire debate over whether or not it should be illegal for adults to engage in consensual acts in private is futile.
And Santorum's argument about "consent and privacy" would be about laws that are impossible to enforce.
So who's REALLY creating a strawman?
Private consensual acts include incest. They also include bestiality. I take it you're against a prohibition on both? (And don't try the bogus 'animals can't consent to sex' argument; they can't consent to being killed and eaten either, but we do that)
We pass many laws whose prosecution is made very difficult by the constitution or sheer practicality. Of all the instances when someone exceeeds the speed limit, how many are prosecuted? 0.01%? Do we argue against speed limits because to really enforce them we'd need massively intrusive action by law enforcement? Nope; we prosecute the speeders we catch, and hope that acts as a general deterrent.