My thoughts on this are, you aren't killing it. You are just releasing it into the wild. If you really want it back bad enough, you can work up for it. You are just setting it free, not ending it's life.

I personally don't like releasing pets that much, because the thought of releasing is kinda sad. It's like you're abandoning them because you don't want them anymore. I know it's just a virtual pet game, but it still makes me sad seeing pets get released.

But I am not one to talk, as I have released some pets before. (Some forcibly released because I had no more space in my stables). Usually instead of releasing, I sell the pets I don't want, and if they don't get sold after a while, i'd probably do a giveaway. And if the pet still hasn't been claimed by another person, then my best choice would be releasing.

Overall, I think releasing is a decent feature, it's another way to get rid of pets if we can't sell them since no one wants them, which I understand if the pet looks ugly because of their colors, or their traits look odd. Releasing can be good in a way if you need space, and besides, I think someone said it before, but if you don't have the money to feed your pets, why let them starve? They'd be better off released so they don't suffer. I admit, I been there before because when I was new to the game, I didn't have much gold to feed my pets. If you can't take care of them, you might as well release them or give them to someone who can take care of them and give them a forever loving home.