2> Knowing this, those who oppose us will do so more aggressively, and they will not do so on the field of battle - they will use other means. (i.e. terrorism.)
3>It is better to have nuclear weapons (N. Korea) than to not have nuclear weapons (Iraq). Failing that, it is better to attack first before you are attacked yourself.
4> A divided Arab world / Europe / Asia can easily be cowed by the US. Therefore, it is better for other parts of the world to unite in ways that oppose US goals overseas.
5> Opposition to war is nice, but in this case it was too little, too late. Opposition next time will begin sooner, and will be more proactive in nature.
6> The incentives for this war that other countries thought the most unjust (oil, US multinational development, etc.) will be the exact same incentives that will be most harshly opposed and undermined in the aftermath, not only by the UN, but also by the Iraqis.
7> A democratic Iraq would be seen as a great way to bring about Islamic law, which is supported by a great many Iraqis, including Iraq's religious leadership. It could also be used to strip US multinationals of any claims they might have to a future Iraq.
8> Just because the Shi'ite population didn't want to fight for Saddam doesn't mean that they won't be willing to fight to remove the Americans if they overstay their welcome. Their spiritual leaders have already said as much.