Other examples that come to mind are the overthrow of the Talibans in Afghanistan and the Nazis in Germany and military intervention to save Bosnians. In other words when a regime is so evil that it engages in ethnic cleansing and mass genocide, and does not allow the slightest dissent but uses maximum force to crush protests, there is every justification for a military intervention to save fellow human beings.
If Gadaffi and his clan regain the control of the rest of Libya, there will be a massacre. If the world sits by and allows Gadaffi to bombard its own people in order to survive, it will send a devastating message to other dictatorships, use maximum brutality, do not give any concessions and you will survive.
Gadaffi's survival will embolden the rest of the dictators and will mean long term misery for people living under tyrannies. Military intervention in Libya to stop the madman Gadaffi is well and truly justified.