Prior to 9/11 we did not believe those little countries could do much to harm us so if they had WMDs we weren't too worried about it. But after 9/11 we learned that the Arab terrorists could cause us great harm so WMDs became more important. We could not take a chance that these weapons could fall into the hands of Arab terrorists. I believe this was one of many reasons Iraq had to be dealt with pre-emptively. I also believe that if we don't do the same to other countries in the region we take the chance of these organizations, supported by many countries of the region, will get these weapons to use against us. Imagine the devastation which could be caused by terrorists using several dirty bombs in the United States. Would you want one to explode and irradiate your town?