Scalia believes basically, that he needs to psychically transport himself back to 1781 and figure out what the framers would think of a due process issue. He would oppose the end of slavery, and women's suffrage on the grounds that the framers opposed it. He would oppose homosexual rights because the framers opposed it. Basically, it is a sound position, but it is not a universal one.
Others believe that trying to divine how James Madison believed about internet porn in libraries is ridiculous because there are several angles legally culturally that the founders didn't have to come to grip with 200 years ago.
One can agree with either position without accusing the other side of bad faith. I think there is a subtle difference between Thomas' views and Scalia's views. Thomas wants to limit the constitution to it's bare bones, but Scalia is more into the philosophy of the framers. They came to the same decision, but for different reasons. They often rule the same, but not due to exacting philosophies.
Both Scalia and Thomas would have voted for Dred Scott. Scalia would have argued that the framers didn't believe Slaves were equal to whites therefore they weren't. Thomas would have said that the document didn't protect blacks, even though it should, so with reluctance he had to render his verdict the way he did. I much prefer Thomas' outlook than Scalias. Any prejudice of the framers, Scalia takes as his beacon of truth. Thomas looks at the document, and reads it on it's face, without prejudice.
If the framers said for example, all people who are born here are citizens, but later in non binding letters said that what they really meant was those who were born of citizen parents. Scalia would give that more weight than Thomas would, because that isn't what the document says.
It is a subtle difference, but i think it is powerful.
As for equal protection (assuming that it does also mean equal treatment - which seems to be the prevailing doctrine), there's simply no violation in the Texas statute. It simply outlaws sodomic acts between people of the same gender. It doesn't distinguish between homosexuals and heterosexuals - two heterosexual men commiting such an act would be punished the exact same way as two homosexual men doing it.
With regard to your more general questions of constitutional interpretation, I think Scalia's approach has the most merit. One needs to look at the words of the document, and to look at the historical context in which those words were written, in order to deduce their meaning. To me, that's the most commonsense approach. Yes, it would mean that in some ways, we'd see the Constitution as less than perfect. That's why we have amendments (such as the 13th, which outlawed slavery, and the 14th, which provided some protections against excesses by states). But simply having judges rewrite it because we want it to say something different is not the way to go. That gives them way more power than they ever should have.
One can agree with either position without accusing the other side of bad faith.
I don't know about that. Your point about internet porn may make a certain amount of sense, because that's truly a new issue (though we really need to use the older principles in dealing with it to every extent possible, until we decide to come up with new laws or constitutional amendments). But the sodomy issue is no different now than it was when the Constitution (and the 14th amendment) was implemented. If the Constitution didn't protect it then, then it doesn't protect it now. I think even those justices who voted in favor of this ruling, when pressed, would acknowledge that they were basically ruling that the Constitution had always prohibited these types of laws, and that they had only now just discovered it. If instead they were to say that the Constitution had in fact changed over time, without an amendment changing it, then they'd basically be admitting that they were acting in bad faith, and I think most of the legal community, on both sides of the issue, would agree that they were.
Well, sorry for the long post, but sometimes, when you take a whack at a beehive...