Good point. Personal blindness to ethnicity/skin color is a wonderful thing. When you see someone as a human being rather than solely as a [skin color] person, you've managed to move past silly differences like that, because those things are irrelevant. They say nothing about the person's character.
The problem is that there are still people who gauge the value of others based on mere skin color, and as long as that's a problem, such form questions have to exist, if only to ensure that people aren't discriminated against for something which has no bearing on the content of their character, or the value of their skills. I can't wait for the day when such questions are no longer needed, but for now, they have to stay.
Still, I do like the idea of "irrelevant" being shorthand for one's derision toward people who base their judgments on another person's skin color, gender, disability, or orientation. On a form, though, it's got to be there.
Although I have been mighty tempted to check a box other than "White", and then show up for an interview. I don't think it would end well, though, so I doubt I'll ever try it. I wanted to try something like "Pacific Islander", and then tell them I lived on a small island just north of Antarctica, way far into the south Pacific. I'd have a great backstory, too.