In general it is not the fact I disagree with you philosophy on politics in general, but rather I don't agree with your belief the Labour Party under Brown and Blair has been any better than under Major and Thatcher. It is in the interest of anyone who is socially and economically progressive to reject any government coalition with the Labour party while it continues to betray them. British politics is ridiculously tribal, which it why the Liberals did not get the support the opinion poll suggested they would.
Hence, it would be in the interest of progressives for a David Cameron minority government, his government would certainly fail and Labour would be forced to go back to its traditional values. Cameron would have his hands tied and would find it near impossible to carry out any of his proposed savage spending cuts.