How do a people simply 'decide' to overthrow a regime?

Perusing the Daley Dozen led me to this post on Jim Murphy's blog. As a firm hawk when it comes to Libya I disagree with Mr Murphy and Robert Gates on a lot, but this post isn't about my approach to the war in general. Rather, it is to allow me to express my distaste and frustration at a certain attitude one often hears from anti-war sympathisers. To quote Mr Murphy:

"Gaddafi is a tyrant, but it is up to the people of Libya to decide what happens next in their country and not for any single foreign government."

This attitude of 'let the Libyans sort it out' can be read one of two ways. The first is the sort you hear from isolationists, and carries undertones of 'screw them, who cares?'. That is an understandable, if not brilliant, attitude to take. But one also hears this argument a lot from left-wing and dove sources (Mr Murphy is at least one of those), and it makes a lot less sense coming from them.

Sure, it smacks of the wonderful post-imperial world of respect for nation states and aversion to western 'imperialist' involvement in the internal affairs of foreign countries, which must seem superficially enticing to some. But think about it a little harder and you run into the realisation that, when it comes to well-armed dictatorships and effective police states, the idea that the Libyan, Iraqi or any other people can simply 'decide' what happens next in their country is palpably absurd. The mechanism by which they might make such decisions is called democracy, it is the absence of democracy that defines dictatorships, and it is dictatorships that we intervene in.

So what if Muammar Gaddafi's army does storm Benghazi, after shifting to a focus on infantry and irregulars to counter-act the effectiveness of the allied airstrikes in neutering his armour and airforce. As his troops round up the Libyan People's Army and their supporters and then murders them, does that represent the "the people of Libya deciding what happens next in their country"? If the regime is nothing more than a house of cards and the people have had the capacity to choose to replace it for the last forty years, does this transform them from its victims into its partners?

Setting aside any other consideration, the idea that the subjects of a dictatorship can simply 'choose' the destiny of their country without western help is insulting to its victims. If you want the west to play no major role in assisting the people of Libya towards fairer, more representative government then that's fine, but please don't try to make out you're doing them a favour.