Holy crap, I had that same experience recently. The guy started by saying he wasn’t “white” because he had some Indigenous ancestry (or Indian, as he put it) and distant relatives from South America.

Then he tried that same argument, claiming race wasn’t a thing. It was amusing because he pulled two contradictory whitesplainers in one go: “I’m not white because I got a trickle of non-white ancestry and we’re all one race anyway.”