I believe the US has been kicked out before, and maybe Trump wanted the US to leave before we could be kicked out again. They've always had problems with human rights abuses in the USA, and they appear to be getting worse instead of better.
But just like the USA, the UN is "do as I say, not as I do." Given how ruthlessly they have come down on those exposing brutal military treatment of civilians by "peace keepers" and the sex trafficking (that includes kids) in which the UN officers, peace keepers, and bureaucrats were involved with from taking bribes to being paying customers, I can't see their HRC as anything other than symbolic at best as a commitment to a goal as unrealistic as a commission on reaching Alpha Centauri (heck, the latter is more possible to me than a truly just and humane society--and btw, I don't think humans will ever reach Alpha Centauri, we'll destroy ourselves, or at least our infrastructure, before that can ever happen).
There are a handful of small nations that MIGHT be truly just & humane, but such would only be guesses on my part. I expect that they're just closer to just and humane than most other nations (including the United States, but the USA would also have many other nations soundly beat in this regard) so that the difference between all the nations of Earth is one of degree more than kind.
While I can entertain the possibility that we might get a little better than we are now, I simply cannot believe we'll ever be close to the Star Trek ideal of society (and I've heard some likely interpretations of the dark underbelly that surely exists in the society of "shiny happy people" in the Trek-verse, and they could easily adapt a Firefly like series to it, but I digress). Relatively speaking, our world (at least places like the United States and many European nations) have been enjoying an unusually peaceful and just times...but such times are aberrations, and it should not be a surprise that it's falling apart now. The only surprise is that it lasted as long as it did (and I think Cold War fears and nuclear issues have caused people to reflect on humanity's course of action).
