When people celebrate the death of an enemy leader (e.g. Bin Laden) who sought to destroy them, they're fools, for another, more capable leader may step forward and bring defeat to those who thought they'd won a great victory.
When people celebrate the death of one of their own leaders, no matter how much they disagreed with and despised the leader in question they're scumbags plain and simple, the only exception being when the leader has given them ample reason to celebrate their death - ample reason being the murder, manslaughter, or outright oppression of the citizenry. Maximilien Robespierre, Benito Mussolini, Pol Pot, Joseph Stalin, Adolph Hitler, and many others all provided ample reason for their people to celebrate their death. Margaret Thatcher, the Iron Lady, was not one of those blood-soaked tyrants. Even those who hated and despised her the most do not have anywhere near enough reason to celebrate the death of one of freedom's shining lights.