Don't teach them kids to waste water rinsing dishes! The dishwasher works most efficiently if chunks of food are removed (scrape into trash), but not rinsed.
Comparing it to food doesn’t make sense because food has to be planted, watered, fertilized, harvested, and transported. Water that falls into a local reservoir takes a negligible amount of energy by comparison.
It may be considered safe to use to water your lawn unless it is too acid, but you should not drinking without treating it first. Especially if it has been collected and stored in a reservoir.
Then again food literally grows on trees, you just have to collect it.
Point is most of the time dishwashers do not run on rain water but on drinking water which is a scarce and vital resource so we ought to avoid wasting it.