For this reason, contrary to conventional wisdom, a victory by Rudy Giuliani would strengthen even the socially conservative agenda in the long run.
Perhaps a more likely result would be to take the volume of the discussion down a few decibels. If a New York Republican wins and makes a nod in the direction of social conservatism, a lot of the noise from Northeasterners about Texas or Alabama and from Southerners about New York or Massachusetts dies out.
As to what the long-term effects would be, I can't begin to say. I doubt you'll see a final resolution of these culture wars either way. The drift on some questions is to the right (abortion), and on others (homosexuality, stem cells) to the left.
A bad President or candidate could lose things for his or her side, but there are limits to what a good one can do and how far a President can go even if he's committed to a cause. The question about Rudy is whether he'd been one step back and two steps forward for social conservatives or two steps back and one step forward.
Folks change their minds on social issues via their personal experience, not via government programs, usually, so I am skeptical of the thesis myself.
I should add, that the other point the author is making is that social conservatives should forget about social issues per se, so as to not drive off more centrists seculars (who will not given the culture war stench be willing to consider other conservative ideas outside of those trenches), and just focus on SCOTUS nominations. Assuming that they believe Giuliani is solid on that issue, some will buy into that logic, and some will not.