Senior officials in the Reagan administration elevated the right to intervene to the level of general principle. As one of them said, we "debated whether we had the right to dictate the form of another country's government. The bottom line was yes, that some rights are more fundamental than the right of nations to nonintervention, like the rights of individual people... [W]e don't have the right to subvert a democratic government but we do have the right against an undemocratic one."(Waltz himself was quoting from a 1985 book called Intervention and the Reagan Doctrine, by Robert W. Tucker.)
I suppose the international consensus on R2P is more sophisticated than the rationale explained here, at least, in that it establishes a somewhat more rigorous standard for intervention—one that's based on the ability to relieve human suffering and not on what must necessarily become a subjective determination about levels of democracy. But still we're left with the inescapable reality that decisions about intervention or nonintervention are made in national capitals on the basis of national interests; thus ever was it so.