The answer is that we shouldn't be doing these things, but that the 50 years that have elapsed since the peak of the Cold War, in which both the Soviets and the US had influential voices espousing preemptive nuclear strikes, is in world-historical context the blink of an eye, and it's going to take time and effort for us to shake off the strategies and positioning we (often foolishly) adopted to win that war.
Except for the UN thing. While I agree that the UN is used (on all sides) as a fig leaf, we haven't waited for countries to disobey the UN as an excuse to attack them, but rather used the UN fig leaf as part of a justification for wars that had already been decided on. In the case of Iraq II, that was a grave mistake on our part, but the mistake has little to do with respect for the UN. The UN is simultaneously important and undeserving of much respect.
Except for the UN thing. While I agree that the UN is used (on all sides) as a fig leaf, we haven't waited for countries to disobey the UN as an excuse to attack them, but rather used the UN fig leaf as part of a justification for wars that had already been decided on. In the case of Iraq II, that was a grave mistake on our part, but the mistake has little to do with respect for the UN. The UN is simultaneously important and undeserving of much respect.