Please don't think that I am supporting the idea that persons not properly trained should be teaching dancing. My remarks were in the particular context of sequence dancing, where generally (and there are notable exceptions) the standard of tuition, and of dancing is relentlessly awful, and to be 'qualified' is the exception, not the norm.
Of more general application is the circumstance where someone who has enjoyed relative success in competitive dancesport (and therefore considers themself representative of the 'cream' of the dance community) has the laughable notion that their competitive career has, in some way, equipped them to 'teach', when of course a moment's serious thought would reveal this fallacy for what it is.
Teaching is a vocation, and requires particular gifts. It is useful, but by no means necessary, to be able to dance quite well. I've yet to see a room full of sequence dancers and not wanted to laugh out loud.