The knowledge that someone such as Saddam was in the process of aquiring, developing, or even just thinking of WMD's, is in my opinion more than enough justification to go to war.
One of the tenets of "The Art of War," is to take the fight to the enemy.
GW did just that.
A majority of the terrorist who would like to do us harm are lining up in Iraq to be sent to meet their maker.
And before anyone makes the comment that the war in no way affects me personally, I have several relatives currently in country, on the front lines.