1)The reason we should raise a slogan is because it is *right* and *true* - not because we think we could 'win big' by raising it; or because it's popular. You say that a movement against the intervention could 'link in with the anti-cuts movement to bring down the government'. Firstly, I just don't think that that's true. Secondly - we don't raise a slogan because we calculate that we could make a 'big score' with it! That is no way of doing principled politics at all.
2) You keep saying that we support the bombing. We don't support it - but equally we recognise that it would be daft to call on it to end, as the only logical conclusion of making that call is that Gadaffi would come in and kill all the rebels. We warn to distrust the intervention, to watch it, to oppose any part of it which goes beyond just stopping Gadaffi from annihilating the rebels. But we think you can't raise the call for the bombing to end because, whatever gloss you put on it, that means the end of the rebel movement.
3) Why 'bone-headed'? It's because you're not just wrong; your whole approach is at odds with critical thinking.
We draw a distinction between opposing imperialism "generally" and opposing every single action that an imperialist power does. If you fail to draw that distinction, then you cease to think. You don't have to look at what's happening in reality - you can just see what the foreign ministers in London and Washington are saying, and then decide to say the opposite. It means you become monotone. Nothing needs thinking about - you just oppose everything. The complexity of every situation is ignored, because all you have to say about anything is "no, no no". If that's not a bone-headed way of relating to reality, I don't know what is.