I'm not against putting friendly educational notes on people's cars, but keep in mind that EV drivers and especially Tesla drivers already have a bit of an image of being elitist and out of touch (whether that's deserved or not). Putting a fake citation or a passive-aggressive note might work in some cases, but it risks a reactionary response: "who the hell are you to tell me where I can and can't park?" Once you've gotten someone thinking this way, it's really hard to walk back from that, and you may be moving someone from an honest mistake out of ignorance to intentional action against BEV owners.
I'd encourage you to make sure your notes and conversations are friendly, even if they need to be firm.
Since the spots are generally owned by the adjacent businesses, I'd also encourage you to talk to a manager/owner for that business, and especially make it clear if you are or were being prevented from charging. You don't need to convince them to be altruistic, you need to show them that it's simply good business to make sure that there are charging spots available.
I'd encourage you to make sure your notes and conversations are friendly, even if they need to be firm.
Since the spots are generally owned by the adjacent businesses, I'd also encourage you to talk to a manager/owner for that business, and especially make it clear if you are or were being prevented from charging. You don't need to convince them to be altruistic, you need to show them that it's simply good business to make sure that there are charging spots available.