Because it is very well written, and speaks the truth.
Nah, I'd say it is poorly written, poorly argued, and contains too many errors of fact. It's TRITE anti-Protestantism and anti-Americanism. If I want to read something by an Ultramontanist, I'll pick up something by Joseph de Maistre. He usually has something thoughtful and interesting to say, even when I disagree with him (which is often).
I am not going to sort out various brands of conservatism. What I read by Rao was Catholic apologetics similar to this article and I recommend them to anoyne. Since his political views got him banned from FR, I would not be able to defend them even if I wanted to.
I think your problem is that if you said what you want to say in Rao's defense, you'd probably get banned from FR. And rightly so.
Examples, please.