there are no "excuses" needed to dismiss pacifism, it's a pretty blatantly silly idea with even a cursory look at the evils that have been stopped because their perpetrators were attacked militarily. I still haven't heard how else these forces could have been stopped.
yes, it would be silly for the US joining another acronym'd international body which would very obviously be a forum for European bureaucrats and the third-world to engage in their favorite shared sport (America and Israel bashing). Who would the ICC be accountable to? Can you think of another unaccountable international body that is ineffective in stopping genocide or human rights abuses amongst its members, but great at US and Israel bashing? I can.