It starts out very good and funny and interesting but then you make one of the most common mistakes of creative writing, forgetting that alternatives and communication exist. I like your writing style and most of the ideas you have, but overall that is really not enough.
You want to show how humans allegedly are similar to baby eating aliens in the way of forcing the standards of the adults onto children or the standards of the advanced society on those of the less advanced society but fail to do so because obviously these things are too different.
But mainly, the problem is that the humans do not even try to argue their point to the advanced aliens who evidently completely misunderstand humans.
You try to equate eating babies and making them suffer for a prolonged time, outside factors against the children's will and ultimately causing death to simple discomforted that is largely voluntary because human society cannot function with the kind of life the advanced aliens expect and not adhering to these standards is only met with rebukes, not violence and not death. It is an obvious point but to force a plot development your characters do not even think of such obvious things and also imply that the advanced aliens are hellbent on forcing their standards on humans when they are still at a stage of merely discussing the change of society and you show them to be still very much open to dialog with humans.
PS: showing legalized rape in a positive light without proper explanation is jarring and absurd and does nothing to improve the story, it simply utterly destroys suspension of disbelief while making you really question not just the characters in your story or the human society they live in but also the writer himself. It does not work as simple example of how society changes over time to accept things unacceptable before, especially not you bring up an argument of far less painful and negative things being unacceptable to the aliens.
Seriously, lay off the rape hentai. Consensual hentai is far better in ever aspect.
That aside, besides the rape thing (completely unnecessary, if you just want to show how society evolves to broaden its morals over time there are more than enough other things to use) the main issue is that you force the confrontation only because the characters cannot think of arguments that should be more than obvious to them considering their supposed skills and experience and knowledge.
That is something that can easily break a story in two and I just had to stop reading because it is an obvious sign that the story is not thought through well enough and what follows can never again suspend disbelief because the story is now completely compromised. Once there has been such huge and central evidence of the writer forcing an outcome without even hinting at the alternatives being explored, especially when the alternatives are obvious, the rest of the story can never again be separated from the idea of the writer making things happen for his own convenience instead of for the story to make sense. From then on it becomes impossible to let even minor issues with the storytelling slide because disbelief can no longer be suspended.
This is especially bad in your case because you are trying to convey morals, whether it's what you belief or you just think it makes for a nice thought experiment is irrelevant, which just fall apart under any kind of scrutiny.
I had to stop reading because now that the story stopped making sense it just comes across as some kind of inconsequential and poorly thought through tirade about shifting morals in human society.
PS: all the issues aside, that is a pretty interesting setting.