Hussein's government officials, his diplomats, have been engaged in assorted acts of terrorism wherever possible and they have worked with al Qaeda for years. Iraq's leadership is one which has expansionist aims, which is quite a contrast to Noth Korea's, for example.
TIraq isn't content to just isolate themselves behind a fence and paint aggressive posters to wave at "imperialists."
It's silly to even consider letting a regime like Iraq obtain those weapons. Iraq had the sense to bomb Iran's nuclear facilities, and Israel had the sense to bomb Iraq's. The world would be a good deal better off if we had prevented nasty regimes from getting such weapons- if we had, North Korea wouldn't be the cesspool it is. An ounce of prevention is better than a pound of cure.