Libertarian, the Iraqi's and their apologists, along with foes of the USA, will use any argrument to make their point against taking military action against Iraq. I think Bush's point is that he made his case to the UN for both domestic and foreign consumption.
If the UN fails to act on Bush's insistence, then that is their affair. They cannot stop the USA from taking action.
I am not defending the UN or Israel. But the situation with Iraq is different. Iraq has made war on two neighbors resulting in 800,000 deaths. Saddam used mustard gas on the Iranians, and poison gas on Iraqi Kurds, killing thousands.
These weapons are outlawed under international treaties.
Numerous UN member states, including Arab states, were involved in the Gulf War with UN approval and resolution. The war ended in a cease fire, not a peace treaty.
Technically it might be argued that Iraq is in a state of war with the UN.