"a nation that is doing us no harm, and probably has never done us any harm?"
Gadhafi has been a nut-job of the highest order for decades. Where do you think the IRA got it's weapons from? Where were their training camps? He was the laughing stock of the Arab world for years, banging on about Arab unity and a single Arab state (With him in charge, naturally), until he finally got bored of that and started banging on about African unity instead, where his oil-wealth could buy him some more attention. If the Western world operated to a consistent standard of morality, we'd have done something about him years ago, instead of appeasing him to get access to Libya's oil and reduce our dependance on the Gulf region and Russia , following the debacle that was Iraq.
He is hated and feared by the vast majority of his own people and has stayed in power for years as a result his expertise in playing off one tribe against another and keeping his regular army so depleted that it could never launch a coup like the one that brought him to power. He has funded terrorist groups and civil wars all over Europe, the Middle East and Africa.
We in the West might have an appalling double-standard about which dictatorial regimes we overthrow and which we do business with, but don't delude yourself that he was in any way a good thing for Libya.