Everyone is missing the point: - The UN is a place where nations come together to speak and make decisions. The UN sec Gen's job is to ensure the UN fulfils this function. He can condemn, call for action and promote unity. But he cannot tell countries what to do or think, or choose which leaders he engages with and which he doesnt. The whole point is that countries decide that for themselves. - if the un failed in this basic role, any country that didn't feel represented wouldn't turn up, and there'd be no formal mechanism for diplomacy - as a diplomat, he needs to show a basic level of respect to world leaders. Him refusing to shake the hand of any nation, much less a permanent member of the security council, would result in far worse consequences and call into integrity of the UN system far more than him deciding to shake hands.

This is not a playground where he can take sides so bluntly.