I perhaps have a different take on this having recently returned an animal to a shelter. I have a 6yo son who is allergic to some animals including some dogs. There are dogs he doesn't have a problem with, but others make him break out in hives and have breathing problems. Case in point, a dog we adopted from a local shelter several months ago. We tried our best to have him around the dog before we adopted it, it licked him, rubbed on him, everything. The shelter is very busy and we weren't allowed to tie up one of their workers for an hour just to spend time with this one dog (I totally understand why our visit had to be that short). We took the dog home, took her on a long walk that night and she was an absolute joy, very well mannered and great with our chickens and other dog. The next morning my son was playing with her and broke out in hives that covered just about his entire body (we had given her a bath the night before with the same shampoo we use on our other dog). We knew as soon as that happened that we wouldn't be able to keep that sweet girl. I called the shelter as soon as they were open to let them know and I was treated like the scum of the earth. The woman on the phone berated me for "giving up" on the dog so quickly and informed me that dogs aren't like a pair of shoes. I was incredibly upset. I wasn't happy about returning the dog, but given the medical issue it was causing, I had no choice. I will not put a dog above the health of my child.
We did return that dog with many tears and wrote a letter for them to show potential adopters about what a wonderful dog she was. Several weeks later and after spending more time with her, we did end up adopting a different dog and have had no problems with my son being allergic to her (we adopted a puppy this time on the advice of my son's allergist).
As far as taking a pet to a shelter, I would much rather have a person turn their animal into a shelter where it will be humanely treated for whatever time it gets than to be dumped on the roadside somewhere to slowly starve. The shelter we adopted both of our dogs from even has a clause in the adoption contract that if you are unable to keep the animal for any reason, at any time, you are required to return the animal to the shelter. You are not allowed to find the animal a new home on your own.
I do think that people abandon animals for frivolous and selfish reasons, but I also think it is a shame for everyone to be treated as if they are a horrible person for turning an animal into a shelter. Not everyone lies about their reasons.
Just my $.02.