The Humane Society estimates that three to four million cats and dogs are euthanized in animal shelters each year—about half of all the animals that enter shelters. Do you care? Well, pay up then.
This USA Today story about the growth of "no kill" animal shelters is anecdotal, but it does make one thing clear: not killing cats and dogs is a lot more expensive than killing them. (Same as humans, in that regard.) For example: "The Lynchburg, Va., Humane Society adopted a no-kill policy in 2010 and is asking the city to more than triple its animal-control subsidy to $396,000 by 2015." Other areas accomplish the same goal by increasing their volunteers and outside donations. Either way, it takes a lot of resources, whether public or private.
People like their own pets. In practice, they do not care about animals that are not their own pets. But, also in practice, we all make an implicit choice in these matters. We have kill shelters, where all the itty bitty kitties and luvvy wuvvy puppies are sedated and killed by lethal injection. Or, by paying more or donating our time, we can allow these animals to live. Most of us would profess to love dogs (Look! Look! Look! Look!), and would recoil from killing one personally. But, of course, allowing them to be killed because we don't want to pay for them to survive is ethically indistinguishable. Who pushes the plunger is just a minor detail.
So, knowing that no kill shelters are an actual viable option that is being adopted in municipalities across America, do you feel compelled to demand that the shelter in your town also stop killing dogs, who are just like your dog, and cats, who are just like your cat? Even if it means a slight tax increase? I mean, I don't know, life is about choices, cash is tight, times are hard. But it could be argued that killing pets should be an option that is not on the table, just as we don't kill people once they hit the welfare rolls. It's not some "bleeding heart liberal" or "holier than thou" thing. It's just a simple decision that, just as you wouldn't want your pet to be killed, you're not going to kill other dogs and cats merely for the sake of convenience. It's at least worth thinking about. It's at least worth calmly justifying our collective decision to kill all those animals, without letting the discussion immediately devolve in self-righteousness and name calling.
If you dislike killing animals you should also be a vegetarian.