This was not posted for quite the reason you may think.
The person who posted this note is a disabled person, but someone with a disability that isn’t visually or immediately obvious to the casual observer. So, when she walked away from her car, after parking in a handicapped spot … with a proper permit … she returned to find this note under her wiper blades. Because someone who walks away from a car parked in a handicapped space must be a lazy cheater. Plus ... "A Real Handicapped Person"? That's quite a can of worms right there.
I’m starting to think that the only thing worse than people parking illegally in handicapped parking spaces … or indeed using any accessible features improperly … is people who hassle people with invisible or ambiguous disabilities in a well-meaning attempt to police accessible facilities. There are all kinds of disabilities, and severity isn’t always apparent to the naked eye. If you really feel strongly about intervening in violations, focus on the permit, not the person. If they’ve got a permit, leave it at that, not matter what your instinct tells you.