^ That's the odd assumption, that if you see someone in a vehicle without a load, that MUST mean they hardly ever have a load. It's also a ridiculous stance because WTF business is it of someone else whether that person uses it to haul loads?
You have it completely wrong. Society shouldn't penalize anyone, but if it gets you all upset that they aren't as fuel efficient, then they are paying more gas tax to fund the road maintenance, a disproportionate amount of they aren't hauling a load so they aren't putting more wear on the roads.
They aren't more dangerous to supposed "vulnerable road users", on the contrary they sit up higher with a better view and distraction is the usual cause of accidents, not what vehicle you're driving provided it is not in an ill state of repair. A smaller ICE or EV sedan will still squash a pedestrian like a bug but trying to regulate passenger vehicle size still won't impact commercial vehicles. Making passenger vehicles smaller has historically shown to be more dangerous to the passengers of those vehicles.
So what if they take up more space? That should delight you if you have a smaller vehicle, to make it easier for you to park, have more available parallel parking spaces too due to longer vehicles not fitting in tight spaces.
So what if they get worse mileage? It comes back to being none of your business. Nobody wants you, or anyone else to micro manage their life. Maybe I think you use too much toilet paper and it's destroying the forest, but it's none of my business as long as you're paying for it.
How about posting on Anandtech? Maybe you are doing it too much and using too much power. Surely you didn't think power generation was zero emissions even if done the greenest way possible?
Clearly, it makes no sense to be wasteful in your life but point the finger at someone else. Fortunately we have the freedom to pay for whatever we want within legal limits.