The purpose of a cockfight is to force two roosters to attack each other until ultimately one of them dies or is critically injured. I would certainly classify it as cruel brutality to animals and I think most Americans would agree.
Per Wikipedia, dogfighting wasn't completely banned in all 50 states until 1976, but that doesn't mean it was still considered socially acceptable and mainstream in parts of American during the 60s and 70s -- its probably even more taboo in America than cockfighting because dogs are intelligent companion animals. As MarMema noted, Bear baiting is still allowed in South Carolina under a grandfather clause, and its probably the most brutal of the three blood sports.
In any case, I'd certainly place cockfighting in a similar category as dogfights and bear-baiting -- as a relic of a barbaric era, or as you noted: "activities that have been shunned by polite society for over a century" Cockfighting was once popular in American during the colonial era (I believe George Washington used to bet on cockfighting), but it fell out of favor by the civil war era, and it was outlawed in most states decades ago (despite three states being the exception to the rule), and I can't imagine the "average" voter in Kentucky would find it socially acceptable to have a cockfight. I've heard of public cockfights in third world countries like Vietnam and Peru, but not in places like New Mexico (and keep in mind those are the same countries that find it socially acceptable to EAT dogs. Barack Obama's childhood being a clear example ;-) )
Cockfighting was a major issue in the 2002 Oklahoma gubernatorial election that allowed rural hick democrat Brad Henry to upset Steve Largent.
There was a referendum to ban it on the ballot, it passed by 56%-44%, so a very large minority wanted to keep it legal, it was at least as recently as then in, not nearly as socially unacceptable as dog fighting. I seem to remember it being a plot of a “Seinfeld” (set in NYC) episode once. “Kramer” got involved in underground cockfights. I can’t imagine the #1 sitcom in America having a dog fighting episode.
Anyway, even though the ban passed, it brought out tons of slack-jawed yokels to vote against it, they also voted for Henry who was able to win a narrow plurality with RINO ex-US Attorney Gary Richardson stealing votes from Largent as an independent.
Brad Henry 43.27%
Steve Largent 42.61%
Gary Richardson 14.12%
I agree with you that it’s vile and disgusting and it would be my preference if it were illegal everywhere. Auh2o tells me that banning it in Puerto Rico would cause economic problems because it employs a significant amount of people.