Scarcity of Kidneys: A Physician Making a Child Ineligible for A Kidney Transplant because of "Mental Retardation"

Read this mother's heart wrenching story here of how a transplant physician at the Nephrology Department at Children’s Hospital of Philadelphia has reportedly denied a little 3 YO girl with a rare genetic disorder the chance of getting a kidney transplant because she is "mentally retarded."
Here is a partial transcript of the emotionally charged conversation according to the mother's account:
(Start Transcript)
[Mom]“So you mean to tell me that as a doctor, you are not recommending the transplant, and when her kidneys fail in six months to a year, you want me to let her die because she is mentally retarded? There is no other medical reason for her not to have this transplant other than she is MENTALLY RETARDED!”

[Transcript Surgeon] “Yes. This is hard for me, you know.”
(End Transcript)

Nobody should pretend to be omniscient, or to "play God", and certainly, nobody should revel in "playing God."
While I certainly understand the mother's position, I can see the physician's position although I vehemently disagree with it. I hope to write an extensive post on why I feel this way.
But, the mother reports she offers to find a live donor.

[Mom]“Oh, that’s ok! We plan on donating. If we aren’t a match, we come from a large family and someone will donate. We don’t want to be on the list. We will find our own donor.”

[Doctor] “Noooo. She—is—not—eligible –because—of—her—quality– of –life—Because—of—her—mental—delays”
If the family finds a live donor match from their family, surgeons are able to implant even an adult kidney into a child's body by implanting the kidney into a different part of the child's abdomen. (See here to read about cutting edge research being done at Stanford's Lucile Packard Children's Hospital where they have pioneered a method to keep adult kidneys alive even in small children where blood tends to pool and clot in the relatively large kidney causing the organ to stop functioning.)

Assuming the family is able to obtain its own donor, the transplant surgeon should keep his opinion completely to himself... the family is not getting involved with the transplant waiting list so he should not "play God" and pretend to be omniscient...he should allow the parents of this little girl to do everything they want to keep their child alive.