“...an activity where birds do what comes naturally to them...”
Roosters squaring off and fighting for dominance until one breaks & runs is a natural activity.
Slashing each other with steel gaffs mounted by humans and fighting to the death is not a natural activity for gamecocks.
When Matt Bevin got into hot water for supposedly meeting with cockfight promoters (he didn’t), I watched some cockfight vids. What happens to fighting birds was sickening to watch. And I’m not animal rights but cockfights are sheer cruelty for entertainment.
Cockfighting is so ancient that by now these birds are biologically optimized for fighting with weapons.