Right, but the Superhappies consider the harm and pain inflicted and experienced by humans to be equally needless, because their own existence proceeds without requiring it. They're to us what we are to the Baby Eaters.
Except I didn't see that baby eating was still a factually crucial or in any way beneficial element to baby eating society except for sustaining their way of life.
Pain is an important indicator to us that something is not quite right. I wonder what the Superhappies would do when subjected to trauma due to accident or disease - continue on their merry way until they just die, unaware of the problem?
Emotional pain is also important factor in human psyche as long as the world is not perfect. In a perfect world, there wouldn't be anything to cause emotional pain or distress - but taking the ability to feel pain away doesn't make the world a better place.
Sadness, feeling of loss, or lack of satisfaction will lead to desire for something better. Not being able to feel loss for the death of a loved one would, to me, diminish the meaning of the relationship. Similarly, if someone is in a bad position economically, socially or what have you... if they weren't able to feel unsatisfied, or otherwise have a negative feeling about it, they would never have motivation to improve their position.
The more I think about it, Superhappies being "unable" to feel emotional distress, pain or otherwise, sounds unplausible. Their goal in life would be to have as much lulz as possible - if you put them in a situation where lulz was denied (let's call it a srs bsns), wouldn't they feel... lack of happiness as a bad thing?
Wouldn't they think "hey, this sucks"? Would they feel emotional distress for lack of lulz? Would they feel pain when deprived from their... means of communications?
...actually sensory deprivation never had such nasty connotations before, now that I think of it.
So anyway, Superhappies come across as a bit of hypocritical.
At any rate the key difference in Humans to Superhappies and Baby Eaters to Humans is that what humans do to themselves is an individual decision - the story seems to suggest that humans would have been capable of disabling their ability to feel pain, physical or emotional - whereas the Baby Eaters brutally murder their young regardless of their obvious objections.
Both the Baby Eaters' feeding habit and Superhappies' forced painkiller distribution reduce the liberties of individual.
Which may be a moot point to Superhappies if they see themselves as one individual in some sense, but that doesn't change the crux of the matter.
Eating children and choosing to retain the ability to feel pain are not ethically analogous decisions.