I share your like for Ellen Meiksins Wood's concept of imperialism and critique of Leninist/Luxemburgist versions (as OK for their time but historically specific). But I draw different conclusions. US geopolitical strategy generally follows a police logic - it has no need for direct political domination because economic forces are enough to get what the West needs from the rest of the world - it primarily wants political order, stability. There are of course other forces influencing it, not least ideological ones, but that's the baseline. The logic is to take a pragmatic view of the ruling forces in particular countries and regions - it doesn't have a preference for dictatorship, but if that's what maintains order, so be it.
So that's why I find unconvincing the vibe from some 'anti-imperialist' quarters that the US et al are going into Libya because they're scared of the democratic eruption and want to channel it away from any challenge to 'imperialism'. Besides instability vis-a-vis Israel, Iran, etc, the Western powers have little to fear from the democratic uprisings. For one thing, they seem basically liberal in inspiration and goals, though certainly having to incorporate a number of social/economic working class aspirations as well. But even if they were adamantly socialist, I doubt their economic plans would be anything for the powers to fear, because they would themselves have an abiding interest in keeping the oil flowing.
The one argument I think makes sense on the anti-intervention side is the precautionary one, that it could easily make things worse and/or drag on into another quagmire. But here it becomes a matter of judgment as to the likely outcomes, weighed also with solidarity with the rebels on the ground, respect for their reading of the situation and their request for the intervention.
Mike