Retarded and mentally challenged are two different things!! Mentally challenged is someone born with a problem(s), while retarded is someone who has a brain but can't use it right. Meaning, someone like a drug addict, a thief, a killer...and someone who thinks this is a porn site!
I will never use the word retard on those who are mentally challenged!!!!

"What spirit is so empty and blind, that it cannot recognize the fact that the foot is more noble than the shoe, and skin more beautiful that the garment with which it is clothed?"
—Michelangelo