Many people on HN run on a logic system, many seem to be emotional.
So when someone post some cute puppy that has cancer logical people might flag it. Many puppies die of cancer everyday, we don't hate said puppy but we just like to look at the bigger picture ie curing cancer and perhaps not eating animals if we love them so much.
But emotive people don't get it and I can see it quickly turning into a why do people on HN hate puppies so much conversation.
Plus logical people don't want to look like assholes.
Meh, but who knows maybe it'd create constructive conversation.