I do not care whether or not animals can either feel pain or suffer. It matters whether or not this individual has harmed another human. He has not.
Again, all sorts of animals are treated to conditions in which, if they do experience anxiety, fear, and suffering, then they are certainly experiencing great anguish on a daily, if not hourly or less, basis: cattle, sheep, pigs, chickens, lab rats, horses, etc. Yet, we do not care about this suffering because we take pleasure in eating these animals and understand that is the cost of satiating our desire and appetite. This person may have experienced pleasure while he was torturing his dog and that dog's pain was simply the cost of satiating his desire and appetite for pleasure.
If we are going to allow that causing pain, fear, suffering, and anguish to animals in order to serve as pleasures, then we might as well make that universal, and charge everyone involved in any meat industry with animal cruelty.
Just because dogs are more often pets (i.e., house-slaves, if we are going to provide humanity to beasts then we should then note that we are taking away their freedom of movement/choice/etc. if we are not to treat them as simply determined automatons) than mice, rats, bunnies, pigs, sheep, etc. does not mean that they are qualitatively distinct from those beasts in a manner in which they should be respected as human. They are chattel; they are property; and, one has a right to destroy their own property if they so please.