I think what you’re getting at is “disabled or not, parking on the painted margin is prohibited,” which is correct as far as I know, but I think most people would think about it differently if the driver was disabled.
e.g. Someone with difficulty walking wanted to exercise their permission to park there so that they could be closer to the entrance, but still wanted to leave a wide spot open so another disabled driver could potentially use it. Still wrong, but many people would perceive that differently.
Again, not defending the behavior (and the driver likely wasn’t disabled, just a jerk)… But surely you see how their disability status is relevant in a scenario concerning a disabled parking spot?