BMI is a ******* joke.
How so? If you compare BMI, to electrical impedance, to caliper skin fold, they all come to the same conclusion for about 95% of the population. If you are an NFL linebacker, of course is doesn't apply. You can't point to how BMI fails for fringe users and say it is a joke.
I find that most people who say it is a joke simply don't like the results and are in a state of denial.
BMI was designed to measure large populations, not individuals. The fact that it's being used to measure individuals is a lazy way of seeing where you fit in that population statistic, not necessarily a measure of health.
One of the biggest problems with BMI is that it makes simplistic assumptions about how people's bodies are shaped, and tall people tend to get the short end of it.
People want to dismiss it because it's not always accurate in all cases.
In general, though, BMI is a good measure of population statistics, but nothing you should really pay attention to for people who are taller or athletic. Just remember you're in that 5% group that BMI doesn't really work for
Body fat % is a better number to look at (preferably with skinfold or a tank).