I have a disability not necessarily obvious on some days, use a placard, and anyone who yells at me is engaging in disorderly conduct and possibly assault, and is not protecting handicapped rights, which includes my right to live in peace. If you yell at me like a crazy person, I will call the police and I will press charges.
And as for the "obvious" violations. People would think that of my mother, driving the international that was my parents tow vehicle. She would often have people come huffing in her direction, until she'd drop the walker out the driver's side, lower herself down, and head into Kmart. Someone bench pressing 250 might have problems with their legs. And news flash, disabled people go the the gym. On doctor's orders, in many instances. So, unless you are being a creepy stalker guy following someone around you don't really know.
And, I look perfectly fine. My legs last only so long. I have literally put my hip out because I couldn't handle the wait in line at wally world and ended up in bed for a week. Hopped out of the store on one leg gripping the cart because I could put no weight on the bad hip. Was glad the car wasn't parked in the hinterlands