I'm from New Mexico where cockfighting is still legal in certain counties. I've also attended cockfights.
The reason why people attach razor blades or gaffs (2 to 3 inch long ice pick looking things) is so that the cocks will fight to the death. Betting on which cock will live is the only reason why people go to cockfights.
Cocks have natural "spurs" on the legs to fight other cocks with. These spurs aren't typically deadly. I don't understand why "boxing gloves" would be needed - just outlaw the use razors and gaffs.
Of course, if they did this, the cocks would not fight to the death, and determining the winner would be a matter of opinion. If the government requires the use of "gloves", then the point of having a cockfight will be eliminated. I think people would move to underground venues for cockfights with razors and gaffs.
Here are some of the arguments used to keep cockfights legal here:
Compared to chickens that are raised for food, gamecocks have much better lives. Gamecocks are raised individually. They are given the best food, nutritional suppliments, and medial care available. I have a friend who's parents raise gamecocks, and he often complains that the gamecocks "eat better than" he does. Compare this to commercial chicken growers who feed their chickens other dead chickens. Hens are given hormones to produce so many eggs, they literally die from malnutrition. (These hens are fed to the chickens you eat at KFC). Commerically grown chickens are packed into cages that are barely big enough for them to stand up in. This is their whole life. Gamecocks, on the other hand, have free reign over large plats of land. My friend says that his parents' gamecocks "live like kings".
Compare those conditions to that of pigs that are raised for food. From birth, they are placed in pens that are so small, they can't even turn around in them.
I personally don't think that cockfighting is particularly cruel compared to the meat industry as a whole. Until those against cockfighting concern themselves with the welfare of all animals (and actually do something about it, like stop eating meat), then I don't think they have a particular reason to complain about cockfighting.
Just my 2 cents. Don't hate me because my opinion goes against the societal grain.