basically the UN is a forum for dialogue and we need the big players to be part of it.
Allowing the five biggest arms manufacturers on the planet to decide "security" issues is no different than allowing the five biggest drug cartels in the world to decide "health" issues.
When was this nationalist hokum ever in date? Nationality has always been a piss-poor substitute for actual cultural identities... that's the whole reason classical liberal nation states had to be forced onto people through state brutality.