WOW, maturity is always part of the problem and that is why you always have to be the wise one. They will never understand the rationality or the truth and someone has to be the voice of reason. You can only lead him to water, but you can’t make him drink. But you still have to lead him to water, that is your job. You can’t tell him what to do, but you still must guide him in a way that is offering him information without it sounding like mussar.
So by letting him know that his decision is not fair to the person he is supposed to make happy, might make the light bulb over his head ignite. If not in this instance, then at least in the next one. On the other hand, as long as he is home you can say “As long as your home, let me show you how to do your own laundry, it is high time you learned how”.