Actually that's a very good reason, if not the best one.
Having been that way in the past means it's already tried. And if it has been carried on, it means it has passed the test, and it has proven useful. It also means its not fickle.
Nope. All it tell you is that it has been tried and it works for whoever is in power. Any kind of oppression that works, can therefore be justified this way, including slavery and genocide.
Just because something works, does not mean it is good to do. And in fact, having seen the undesirable effects of a practice may provide all the reason need for discontinuing it in favor of an untried practice.
You are simply arguing against the development of society.
