I somewhat agree.. I think BEFORE buy/adopt a dog, you should consider all of the positive and negitive scenarios that Could/might happen in the future.. A responsible dog owner should make sure they have a solution to all the problems that might arise BEFORE they even consider bringing a puppy/dog home..
Dogs arn't meant to be tossed around like used clothing, they need a stable pack mentality.. But there are some sinarios that do arise that are unavoidable, like when my mom and dad decided it was a good idea to add another Female Siberian Husky to our family a couple of years ago ( when we only had Tikeya). Our Malamute had gone to the rainbow bridge a year before, and they thought it would be nice to add another husky to the family, since we wern't greeving anymore.. '
They bought a red female sibe, thinking her and Tikeya would be best of friends... Well after Makiya went through her first heat, she became very agressive towards other dogs.. We got her spayed and she was still very agressive, Fighting with Tikeya any chance she got (Even in the house), at one point the two girls had $300.00 worth of damage between them, my family never had alot of money so we couldn't afford the constant vet bills from the girls scraping..
So my parent decided to rehome Makiya to some friends of ours.. We were all VERY sad to see her go, we all cried for months.. But she was safe, happy, and Tikeya was safe and happy as well.. We added Oscar (Male, shih tzu)to our family shortly after Makiya left.

Baby (Great dane) was rehomed to us when her owners couldnt bring her with them to Alberta.. Aparently a relitive had died, and they needed to move there.. they didnt want to sadate Baby on the plane, so we took her in.. I am so happy we ended up with her, but although they did not want to let her go, it was what was best for her... I think that somtimes crazy crap happens that you cant avoid it, and you need to find a new home for your pet...
BUT in the case of a dog getting tossed out because it wasnt a good enough at "it's job" is just like getting rid of a dog for chewing/peeing in the house/ not bringing you your paper... It's just uncalled for.