I know I for one don't want the UN to police me. Not with Cuba and China on the Human Rights Council and China is on the National Security Council as one of the 7 members who can veto any motion they want. It has become impossible to censure just about any country for either security or human rights violations since member countries of both committees who are guilty of the same thing shut it down. The US representative tries regularly and as far as I know has yet to succeed in something like 7 years. It's like using the fox to guard the hen house.
So that just leaves the US (or another major country) which then leads to issues of sovereignty. Yes we are involved in the middle east because we have political interests there. What is wrong with that? What right would we have to walk into an area that we have no political interest in and conquer the country just because we don't like how they are doing things? Where do you draw the line? Genocide and Human Rights violations? How are you to do that when the neighbors of countries these things happen in not only don't care they do whatever they can to keep major superpowers away from it. It is almost as annoying as Germany playing both sides of the fence on Iran with their "we don't believe that we should get involved *psst* Hey, US, go ahead and bomb them for us."
Fact is no one country can or should police anything in another country unless it impacts their national security and the UN is to corrupt to effectively police anything but their own political agenda's. The invasion of Iraq involved a coalition of over 35 different countries troops and the support of even more. If you can get together that kind of support for one of your other causes then by all means something can get done. If not what country can go it alone? The US? I fear that many European countries believe just that and are expecting the US to do it for them so they can sit cozy on their little self righteous pedestals.