“Why is this any of the feds’ business?”
I have mixed feelings on this where I do not like to see cruelty to animals at the hands of humans. However I agree with your statement because this is just one of the gazillion overreaches of the federal government. Simply put, this is not a federal issue. Period.
It should be kept at the state/territorial level where if the local culture finds this acceptable, then so be it. In defense of this culture, animals are already by nature cruel to one another, take eating their prey alive for example, or torturing their prey before eating them alive. It’s how nature works.
It was until now. Louisiana only banned it in ‘08. I remember going to a few fights growing up.