If I may quote from post #270: "They're trying to make whites extinct." - f00bar
What does a "vast majority," of DNA mean, exactly? Is that at least 75% European? 90%? Who gets to decide this? What does "european DNA" even mean, anyways? (yes, I know you probably mean "from Europe" in general, but there are a lot of holes to poke in this with a little bit of critical thinking.) How long does your lineage have to be in Europe to have "european DNA?" What about Russians? I think we'd both call them a white people in general, but are they really european?
The point I'm trying to make is not that "white people don't exist" -- obviously people with fair skin are real and there is a genetic basis for this. What I'm trying to say is, as you say, that different people have different definitions for what is "white." No matter how rigorous and scientific your definition is, there are going to be cases where a majority of people will disagree with you on if someone is white or not. A majority of people think that they can identify a white person by how they look. For example, I have a friend here on campus who, for all intents and purposes, most people would call white due to his fair skin and facial features, but he and his family are from Kuwait. You wouldn't know that by looking at him though!
To be honest, this whole conversation kinda reminds me of the whole Nazi eugenics thing where Nazi scientists tried to define the line between "jewish" and "aryan" people through measuring different parts of people's bodies. They needed some arbitrary working definition so that in fringe cases they could decide who they should kill and who they should leave alone, and it's hard for me to not see your argument in the same way. Like, I don't think you mean harm to "non-white" people, but the logical conclusion of your argument seems to be that above a certain % of european DNA someone is "white" and below that same % they are not "white." which seems pretty arbitrary to me. Not to mention the arbitrary nature of trying to define what counts as "european DNA" and what doesn't.