Why Did We Go Into Iraq?

I notice that the left still keeps bringing up the fact, that they seem to think we on the right don't know, and that is that Saddam Hussein had nothing to with 9-11. So why did we go there? What was this noble cause? I like how a former black hawk helicopter pilot who served in Iraq answers the question.

"Before I went to Iraq, I was 100% sure that Iraq had nothing to do with 9/11. Nobody ever tried to tell me that Saddam was in any way responsible for that terrible day. We weren't going there to avenge 9/11, folks. We went there to help prevent the next 9/11. It was the second step in what is sure to be a long drawn out campaign that is likely to see even more destinations in the mideast. If you can't figure that out, and you're still foaming at the mouth over all those lies that were never told- well, then, that's you're own fault..."