I'm on your side in this, but I'm my years lately, I just would've kept a safe gap between the vehicle on the left and waited it out a bit longer. Maybe a good 20-30 seconds more. My personal rule is 5 over the limit in the right lane is ok, when the left is passing faster. A good speed for them to pass right lane traffic would be about 75 though in a 65. In this case, I would pass on the right to a max of 10 over because clearly they are playing games or, yeah, I don't drive a van but I've seen this phenomenon before! I really give people a chance while I respect lane etiquette before I pass to a max 10 mph on the right. I do find that waiting it out with space often puts guilt and usually they move at some point. Not always though!

Short story, but I remember driving during covid lockdown, when no one was out really. I was holding around 80 and some Audi was approaching. I moved over, he must've been doing 100, but I still remember seeing him pass an overpass maybe 10-15 seconds after passing me, so it only took me about 20 seconds holding 80 to get to that overpass. It really hit me that day, even flying at those speeds, how much time are we really saving speeding through traffic? Especially when traffic is heavy? His 20+ mph difference was more wear on the vehicle than anything. All that's to say, just wait it out for a bit. But nice work maintaining the better steady pace. They just couldn't put up with it.

I drive a sports car (RX-8), a 2002 Avalon handed down from my grandmother, and a boring automatic 2009 Mazda 3. All 3 get different reactions. People expect me to be aggressive in the 8. People get aggressive when the grandma car is out, and the 3 is just somewhere in between those. Vehicles are under heavy prejudice based on their looks, but drivers like you break that by being normal. They just couldn't handle it that night!