Perhaps instead of a “please stop the generational insults” message, despite a lack of generational insults, the Mom should say something on this.
All I’ll say is that morals weren't created in the clouds and dropped upon humanity, they are something that have been defined naturally over a long period of time through societal interaction, in a world that hasn’t been as connected as it is today. People in different cultures behave differently, but we only view that as objectively worse or better through our experiences in our own cultures, which is often self-centric and heavily biased. Understanding the above is kind of meta and definitely more complicated than being kind to your neighbor, but just like every other moral was defined through social interaction, so will that be, given time.