"BAWWWWWWWWWWWWWW! Some kids mildly teased me and I can't sleep at night until I can murder them all for it!"
Seriously, I can't figure out if the people who like this idea are complete sociopaths or just raging pussies, because they either have an irrational hatred of children, or they can't handle some immature namecalling that any well-adjusted human being would brush off without a second thought.
Just being mean to you does not warrant this much rage, because if an adult character said the exact same things to you, I am 100% certain you would not be nearly as offended, this is why it is irrational.
Only a miniscule fraction of the people in favor of this mod feel that way because having immortal characters negatively effects the realism, in a fantasy game with magic and dragons, the rest are just bitter little douchebags who think taking this pro child murder stance will make them seem cool. Oh yeah, Bethesda made it against the rules to kill children, but you did it anyway, because you play by your own rules! Society doesn't want you to hate kids, but you do what you want, you are the bad boy that all the ladies love!
This isn't about killing mildly annoying characters that any sane person wouldn't mind, this is about challenging authority and proving to yourself that you are a badass, it's pretty damn pathetic really. Nobody would even care about killing kids if the game allowed you to, it's like if you take a toy from a toddler and they start crying even though they weren't playing with it.
If Skyrim is really so broken and insufferable because it doesn't let you murder children for the audacious atrocity of offending your delicate little southern dandy senses with some laughably weak taunts, then maybe you shouldn't be playing it in the first place. Maybe instead you can sit in the corner and cry all day about the kids who bullied you in grade school.