I think the distinction is that ethnic cleansing is a more general term and genocide is a more specific term. An ethnic cleansing can theoretically not involve murder though this is all a bunch of semantics lawyering and I’m sure conversationally they are often used interchangeably.
lol, ‘my side is the best and we oppose the side with the world deliberation body (UN) as part of it!’ For libs, that should really be a sign for them to wonder, “are we the baddies?” but they won’t.