My (probably flawed) comparison is to the term "fair use". Yes, you can play all sorts of games to make those 2 words mean almost anything you want, but at the end of the day that term is defined by law, not by pedantry.
"open source" has an accepted definition, and it's damaging to society to try to undermine it.
If you think I'm exaggerating, please remember that you can probably thank open-source software for the growth of the Internet, the availability of previously restricted secure encryption and thousands of tools that you probably use to earn a living.