Chavistas: How can anyone say legitimate criticism of Ch�vez if they're accused of supporting "US imperialism"?

That's the whole point. A communist/totalitarian regime run by a dictator can't come up with reasonable arguments to respond to criticism. So they do the next best thing: they attack the person/organization making the criticism with labels, insults and slogans: "apatrida, escualido, oligarca, burges, traidor y lacayo de los gringos" and stuff like that. Anyone who doesn't bend over to lick the boots of The Cowardante and complies with "el proceso" fits into one or more of these categories. That's all they have.