Perhaps not. But as you say, you're opposed to abortion: consider a weird hypothetical. The UN declares abortion to be illegal, world-wide. Would you not only defend the US but lead the military in an aggressive war against the UN based on this one policy?
(The analogy is readily admitted to be a bit lame...)
Lee could easily have led the *US* forces, which would have been far better for both the US *and* Virginia... and his own soul.
Probably so. However, in the analogy you gave, add the idea that UN troops invaded the US to enforce their beliefs. Which would be more important - defending the sovereignty of the US or possibly ending abortion? It becomes a terrible, heartwrenching decision. It's the same decision Lee faced. He chose to defend the sovereignty of his state. History has proven that although he chose the losing side, his motives were honorable and just.