Those are two different responses, @cdwccrn. To be sure, in many or most cases it is best to say nothing and not get angry. But there are also times when a response of some kind is appropriate. As Alfreda says, you aren’t through having something to teach them (and they aren’t through needing to learn) just because by some measure they’re grown up.
But anger does not have to have any part of it (and I don’t think sarcasm ever helps people either). People don’t learn well when they’re all wound up in being defensive. A gentle but straightforward question (“So what are your plans, then?” “And how are you thinking you’ll deal with that?”) and even possibly a direct offer (“Would you like to hear what I think?”) seem more constructive to me if the aim is to help and not to punish.
And most of the time, of course, they will learn the most from seeing the consequences of their actions. If what you want is for them to get the lesson, that’s your motivation for silence.