@ Tsanten Eywa 'eveng
I think the reason for killing him was indeed for revenge, however perhaps it's better off that way. Gaddafi still had supporters and had he been kept alive, they'd have had reason to carry out attacks against the new government. The same goes for Bin Laden. I think the way they have handled his burial is very bad though. Instead of burying him and continuing to be noble about it they have left his body in a city to be photographed by the populace

Taking into account what a great job they made of the uprising, it's sad to see such a .... 'dishonourable' end to it.