Since when has "fair" had anything to do with legality? It is his animal. Bottom line.

You can try to educate someone, but you can not control their actions. Getting bent out of shape about it and berating someone does not actually do anything. It might make you feel better, but it isn't going to change the situation at hand.
I agree that there are too many animals in shelters. Just like I agree that there are too many babies born into bad situations. It is irritating, but it just doesn't pay to get worked up over it. You end up just making yourself look bad.