I think saying that that the parent's statement "comes across" as condescending and rude is taking the principle of charity and presumption of good faith a bit

I think saying that that the parent's statement "comes across" as condescending and rude is taking the principle of charity and presumption of good faith a bit far. It is condescending and rude by any standard of good manners and productive conversation that I care to engage under. If a child learns the hard way that X -> Y I don't berate them and call them stupid for not listening. It doesn't make them more likely to listen the next time. Same with adults, really.