Hi ProfoundPuns and anyone else listening in. Anyone visiting my hubs knows I am an advocate for the humane treatment of animals. But, and this is not a contradiction, I do not find euthanization of an unwanted animal inhumane.
The real answer to this problem lies in a good spay and nueter campaign. Having said that, I have produced a few litters of puppies -- mastiffs -- over the years because this ancient breed should be maintained and improved. There is a big difference in planned breedings of well maintained dogs chosen for their attributes, with families waiting for them and just having puppies because a) you were too lazy/cheap to get your bitch spayed or b) you thought it would be neat or c) you were under the mistaken idea you could make money at it.
How many times have I heard, we let her have puppies because it would be good for the kids to see them born. I bite my tongue so I can't say, well come with me and see puppies getting dead.
I don't believe this is a problem we will ever control, or not for a very long time. Until then, the shelters of all sorts and the rescue organizations will coninue to do their best. And when that isn't good enough, it is far better to give an animal an easy death than the alternative of a life of want and dispair.