Pearls to pigs.
In 90% of the situations I've came upon my 35 years on the saddle it would be a total waste of breath and maybe even me coming across as an arrogant-know-it-all, and for nothing. So unless it's something safety-related or if I know the person to some extent, I just hold my tongue. I came to the conclusion that people only want to hear what they want to hear, so there's really no point in trying to enlighten someone. But of course if the person asks for advice then it's a different ball game.