BMI is a perfectly valid first-order approximation of appropriate weight ranges for the 95% of the population who are not body builders.
It seems similarly unreasonable for most of my friends and family.
When I weighed 160, I had slightly defined abs. Similar to what you would see on someone with 10-15% body fat.
The existence of a lot of overweight people in the US doesn't change what the words "overweight" and "athletic" mean.
What is not objective is looking in the mirror in some lighting and thinking you look pretty good. That's a subjective measurement based on objective reality. Your body might distributed fat in a way that's relatively aesthetically pleasing -- mine does too, it hides it all in the thighs, and people think I'm way more in shape than I am -- and that's not the same thing as being healthy.
Traditional BMI makes short people think they're thinner than they are.
Maybe they are crude. Maybe there are better alternatives. That doesn't make them unscientific.
Those who double down on IQ as being infallible have something to lose if it's proven to be hack. And history is not on your side here.
No it hasn't.
BMI doesn't work for three groups of people: it makes very tall or very athletic people think they're fatter than they are, and it makes very short people think they're thinner than they are. But, as GP says, that's less than 5% of the population.
History is very much on the side of IQ realism. Ten years ago people were denying that a general factor of intelligence existed at all, now it's down to nitpicking or argument from ignorance.