BMI does not take into consideration body composition. It does not differentiate weight from muscle and weight from fat.
And if you see most non-offensive linemen in football, they're probably the most athletic athletes in all of pro sports.
In what other sport do you have athletes who can run in the olympics, do international weightlifting competitions, be blackbelts in various martial arts, be in ballet, be wolrd-class jumpers and can do marathons?
In what other sport can those athletes be all of those?