Hmm, must be demographic in specific countries, here in Switzerland the biggest a-holes IMHO are Tesla drivers, not all of them obviously (some of them drive ridiculously slow which is another danger), but it seems that tailgating is shared among many of those. Full gas & brake style of driving. Second biggest in my experience are... spread quite evenly across the brands, crappiest old french or italian ones are often a bit worse for some reason.
When frequently driving through France, on my previous BMW 3 series sedan I was facing tight swirls and 1m tailgating on otherwise empty highways. They eventually lose interest when they see no reaction and see me driving according to rules, but its stupid and needlessly dangerous for everybody. So what is common trope of arrogant BMW drivers was actually, every fucking weekend over a decade, experienced by plethora of brands driven by french drivers, on BMW which was driving way more civilized than they were. Not even anyhow fancy one, no striking colors or designs on a freakin' V6 diesel.
Switched to another BMW, 5 series wagon, and absolutely 0 of this, ever, in 4 years.
But then again, in Switzerland there are tons of BMW, Mercedes, Audis etc., often compromise >50% of the traffic around me, and the idea that all BMW drivers behave like that is stupid. In fact traffic normally goes OK, in the morning rush hours I don't see any brand being particularly worse (apart from that Tesla, but maybe I had back luck on new drivers enjoying all that power).
I guess different people tend to go for different cars. Also, say grey BMW 2 series is as uninspiring, boring and slow car as it can be, thats more a granny car than anybody else.