Exactly what on earth does a fish's intelligence or bond to humans have to do with it's ability to experience pain and suffering? Do all of you making this argument think the mentally retarded don't feel pain as acutely as someone with a PHD? Seriously, ridiculous. The issue here isn't the intellect of the animal, the price of the animal, how friendly the animal is, or any other of the inane BS that has been used to devalue bettas. The issue is that the animal is being needlessly exposed to pain, suffering, and sometimes death so people can get their jollies.
About the only point I agree on mentioned here is that dog fighting is a greater sociological issue and thus probably deserves a stronger legal penalty. Drugs and arms dealing are common at dog fights, and as mentioned fighting dogs are bred and trained for a viciousness (especially in modern dog fighting) that makes them dangerous to humans. Policing these acts and dealing with the dogs is costly to taxpayers as well.