Timing is everything. Qaddafi was not killed in retaliation for his attacks on American servicemen in Berlin in 1986, or the downing of Pan Am 103 over Lockerbie in 1989. He was not killed for his central role in the USSR's terror networks going back to the 1960s and 1970s. He was killed after coming over to our side of George Bush's "war on terror" in the final phase of a civil war in Libya in which his regime fought al Qaeda affiliates.
Horrific as it sounds, Qaddafi was killed because we and our NATO allies joined the other side -- the al Qaeda affiliates.
Lawrence Auster elaborates on why the event rankles:
Kaddafi never violated his agreements with us and never became a threat to us or our allies. He spoke in the warmest terms of the United States and of Obama. Yet the instant that people whom we chose to call democrats rose up in rebellion against him, our ideology and what we perceived as our political self-interest required that we side against him. We attacked his country, bombed his military and his government, bombed his residence, drove him from power, and now we have killed him.
I will not become a moral relativist and make the despicable statement, which some commentators on the anti-war right have made, that the U.S. is as immoral as the Soviet Union. Nevertheless, there is now significant and terrible overlap between the behavior of the U.S.S.R and the behavior of the United States. We are not a moral state; we are not a state under the rule of law. We are, as Solzhenitsyn said of the Soviet Union, an ideological state, a state that will do anything, violate any agreement, betray any ally or friend, tell any lie, cover up any truth, in order to advance its ideology and its power that is associated with that ideology.
In betraying and killing a foreign leader with whom we had made peace, we have taken on terrible karma. I tremble to think of how that karma will manifest itself against us in the years to come.