Ok then Ceallach I wasn't going to say anything, because I think in this situation the kid didn't protest, but since otherwise the thread would be a repeat of I agree to the endů.
In general I think someone can ask others to help out, but you can't make them. I don't mean that it's only bad if you drag them by the hair to the dishwasher, but more along the lines of commanding or dragooning someone into helping not being okay.
I totally agree that everyone should help and it is right that everyone pitch in. But if a kid says they don't want to and you now know their parents don't want them to, I personally think that after asking and maybe explaining the fairness aspect of it, one should stop.
Well, I do think you have a point, except I want to note that the "kids" are college age, so I personally don't think that what their parents want has anything to do with it. Definitely if we are talking about 12-year-olds or something, one should take the parents' wishes into consideration, even if one disagrees with them.
Also, I think the way the OP described the situation, the older generations of adults were right there when she asked for help with the dishes, and no one said anything--not, "What a great idea!" but also not, "Oh, don't bother them with that." In this situation, if there is a higher authority, it's not the young adults' parents but rather the hosts, whose house it was and who did most of the meal prep. If the host
didn't want the young adults doing dishes, or otherwise felt the OP had overstepped in their home, they
need to say something, and the OP would have to abide by that.
I do think it would be impolite to "badger" someone into doing something, even if they "should" be doing that something, especially if you're in someone else's house. I don't get the feeling the OP badgered anyone, I'm just saying in general. If it's your own house you can set consequences or choose to not invite that person again, or even ask them to leave; but in someone else's house I think you can ask, maybe point out the logic, but if they just outright refuse, I think you have to end there in order to be polite. It's up to the host to enforce more strongly if they want to. And then beyond that family dynamics come into play--like if the relationship
is such that you can take the person aside and say, "Okay, stop being a doofus," and have that go over well. Not really recommended with someone you don't know well, though.