The Trotksy quote is a good analogy for why the workers' movement here should be for the arming of the Libyan rebels. We shouldn't support even critically what imperialism is doing now though. The imperialist bombing of Libya risks driving some parts of the population into support for Gadaffi or at least a distraction from the task of overhrowing them, leaves the imperialists in complete control and able to impsoe terms on the rebels. It means that if there had been any chance of working class expropriation of the oil fields and moves towards socialism that they will be blocked by the imperialists.
When Gadaffi controlled planes, troops or tanks are taken out that is good whoever it's by but it would clearly be much better under the control of the rebels. Overall though the intervention strengthens Western strategic interests in the area. Given the choice of immediate death from Gadaffi or a slow strangulation by imperialism it is not surprising they chose the latter nor can such a choice be condemned- but we should be for the rebels being armed under democratic Libyan workers' control.
I don't specifically know any progressive workers' blocs- I know of individuals who have gone to Libya open to different ideas including socialist ones. I know that if the Libyan rebellion had defeated Gadaffi under their own control albeit with outside weapons and aid that the liberation of a society produces tremendous opportunites. Those opportunites are now very much truncated. That doesn't stop support for the rebels in their fight against a murderous dictator anymore than we check the politics of those facing attack or murder from fascsits.