I happen to agree with you that Rick Santorum was referring to liberal Protestants who have denied the Gospel.
But I'm not sure why you want to get into the doctrinal differrences between his Catholicism vs Protestantism.
Already a huge number of Protestants...Evangelicals....have searched their hearts and with discernment have chosen to support him.
For whatever it's worth, I voted for Santorum in the Missouri primary last month and barring something totally unexpected I assume I will be voting for him in about a week in the Missouri caucus.
You ask a valid question about why I'm raising the issue of doctrinal differences between evangelicals and Roman Catholics.
If I read Unspun correctly, he's trying to argue that Santorum attacked Protestantism in that speech and therefore Bible Belt conservatives in the South shouldn't support Santorum. That's a misreading of what Santorum said.
However, I believe it is important that we realize that Santorum probably **HAS** said some pretty negative things somewhere, not just about Protestant liberals but about Protestant theology as a whole. I would not be at all surprised if somebody unearths a tape of Santorum attacking Protestantism as defective theology. That doesn't bother me. A faithful Catholic **SHOULD** have doctrinal problems with evangelicals and vice versa, but both evangelicals and Catholics can agree on enough that we can fight together in the political sphere even if we cannot be members of the same church.
Maybe that's a surprise to liberals, but for most people in the pro-life movement, we learned long ago that we need to agree to disagree. Conservatives aren't as narrowminded as lots of liberals think we are when it comes to understanding important differences between the standards for participation in the church as communicant members and in the state as voting citizens or elected officials.