If you don't care that Iraq didn't have WMDs, you should.
All I can say is do you really believe that the Iraqis think that we are "freeing" them? We killed thousands of people there when we rolled in.
It's not that I don't care about WMD's, but I do think the war can be justified completely on the WMD issue, or completely aside from it.
Hussein was required to submit to weapons inspections by the United Nations, as a condition of his surrender during the Gulf War. For the decade that followed, though, he engaged in a game of deceiving and frustrating weapons inspectors, and kicked them out of the country several times.
It is NOT the responsibility of the United States to gather infallible intelligence on what Iraq was doing; why it was refusing to comply with inspections. It WAS Saddam Hussein's responsibility to fully comply, and prove to the world that he did not have WMD's. He simply did not do that.
Knowing his history of using WMD's, and given his current behavior, the common-sense assumption is that he's being secretive because he has something to hide. When you can't deal with certainties because Hussein has made that impossible, assuming the worst is the only responsible action. But I don't mean to suggest that our decision was made on blind assumptions; there was very convincing evidence of his WMD programs.
As David Kay, the Chief Weapons inspector said after his resignation, "It was reasonable to conclude that Iraq posed an imminent threat. What we learned during the inspection made Iraq a more dangerous place potentially than, in fact, we thought it was even before the war."
Kay also reported that Iraq attempted to revive its efforts to develop nuclear weapons in 2000 and 2001, but never got as far toward making a bomb as Iran and Libya did. He said Baghdad was actively working to produce a biological weapon using the poison ricin until the American invasion last March.
All the evidence that we have points to one conclusion: Hussein was feverishly working to develop WMD's, if we didn't have them already (a possibility that I'm still skeptical about). He wanted to develop nuclear weapons, and given enough time, he eventually would have been successful, or obtained one on the black market.
You said that the U.S. has to learn international diplomacy, and not brute force. On the contrary, you should be applauding the U.S. as one of the few countries willing to enforce INTERNATIONAL LAW, and prop up the United Nations as though it were a relevant institution.
As to your other point - "We killed thousands of people there when we rolled in." It's true, we killed thousands of soldiers in the invasion (but actually, we allowed most to surrender. Perhaps if we hadn't been so careful about sparing the lives of Hussein's loyalists initially, we wouldn't be having so many problems today). We did NOT kill thousands of civilians. If that's what you meant to suggest, it's simply not true.