I think it's genuine. If it's also some sort of Slytherin ploy I haven't caught any hint of that.

On a few rare occasions that he's let it show, he is so very very angry about Lucius and Draco that I think the only thing holding him back from direct action against a list of people is that "Our Lord" would object to open civil war amongst his "Brotherhood" rather than the cold war they have now. I know that's cold comfort, but if they go after Percy I think it would only be as part of a whole domino series of actions. Nott, Mulicber the Remaining and a few others.