Considering King Triton’s “advice” amounted to “no surfacing even when there is no humans in proximity” (you know that merpeople are more likely to see us coming before we see them coming, right?), and, I should add, he implied he wanted to commit genocide against humans (the whole “One less human to worry about” thing), I’m pretty sure that is “advice” I wouldn’t even obey if my own parents gave, heck, my own parents or even grandparents would not obey regarding THEIR parents, and I share my parents politics in that I’m conservative. Heck, there are a few people who actually went against their parents in Nazi Germany by fighting AGAINST the Nazis, and NOT for the Communists either.
Besides, at least Ariel actually worked hard to save her dad and avenge him and tried to fix her mistake, which is against what post-1970 would advocate (if anything, post-1970 would advocate having kids act like, say, Francis from Malcolm in the Middle).
Let me put it another way: Alucard in the Castlevania series often ignored Dracula’s “advice” of committing genocide against humanity after his wife’s death, by your logic, this was trying to promote communism even when it’s clear that unlike Dracula, Alucard was actually on God’s side (when if anything, adhering to communism would have Alucard obeying Dracula and trying to wipe out all of humanity. Sort of like that horrible Rise of the Planet of the Apes movie).