I’m not saying Putin can be talked down from his current course of action, but if you start expelling every corrupt country from the UN then it loses any semblance of value. If there were no Russia, China, Iran, and North Korea present in the UN (not to mention the less imposing, but equally disturbing countries), then what is a UN resolution worth? If lots of countries are unbound from the UN charter, then how much weight can it ever have?
Plus, there are plenty of Central and South American countries and Guantanamo detainees that could argue that the USA should be kicked out of the UN. If that happened, how much legitimacy could the UN possibly have?
Sometimes pragmatism has to trump principle. I think this is one of those situations.