Rachel:
I think your letter to your parents is wonderful. I do hope you can convince them to rescue a pup from a shelter. As Karen, the founder of Pet of the Day, said "There's nothing wrong with the dog, most of the times it's the owner's fault." There are, sometimes, circumstances beyond a person's control that require that a dog be turned to a shelter. But in the majority of cases the reasons are so stupid, or mean, that make your hair stand on end. How about turning in a pup because his color doesn't match the new furniture. Believe it or not, it happened!
If your parents want a specific breed, there are rescue organizations for every breed on the books. Take a look on the Web and good luck. Please let us know how you are doing.