testosterone-fueled aggression and territoriality between roosters

BIRDS ARE NATURAL FIGHTERS

While birds will fight over food, territory or mates, such fights are generally only to establish dominance within a group (the pecking order) and seldom result in serious injury. This natural behaviour is quite different from what happens in staged cockfights, where the animal’s will to survive is exploited. Winning gamebirds are a result of artificial selection—intentionally bred for maximum aggression.

COCKFIGHTS ARE PART OF OUR CULTURE/HERITAGE
While it is true that cockfighting has been practised for centuries in various countries, including the United States, "old" does not necessarily mean right or even acceptable. Heritage cannot be a defence for inexcusable, intentional abuse for the sake of entertainment. Cockfights are centred on animal suffering and apologists try to dress it up as tradition to disguise and excuse the egregious cruelty they inflict. By passing strong laws against animal fighting, federal and state governments have declared that it no longer has a place in our society.