This is a subject that will always get responses from both sides. As many have indicated a disability doesn't mean its noticeable. One doesn't have to be in a wheel chair, walking with a Cain or walker, or limping. Many disabilities are unseen. My wife is one. She has more than one health issue that makes it hard for her to do things you and I take for granted. Cancer is one. On her better days she parks like everyone else. On the bad days she righty uses her handicap.
She has more than once ( usually at Costco for some reason) been verbally abused and yelled at by other people ( usually men). I wish for one time they would say something while I'm with her.
Sure it gets abused, and that is a problem. All I have to say is there is someone always thinking they are better than everyone else and will put themselves above everyone no matter what. I don't hear people complain about those who park right in front of the store clearly marked no parking and run inside to "grab something", all the while pedestrians and cars have to negotiate around them.
People using a handicap spot, we never question it as you never know. If you're using it illegally you a lazy inconsiderate bum. I think handicap people get abused by people more then someone abusing the privilege.