Well, that would be a new one for me as I can't recall ever being passed by an RV in any of my non-towing vehicles. Heck, it is rare I am passed by any RVs even when towing. Sure, every trip whether towing or not there is bound to be someone driving (what we would consider) insanely, I guess it's commonplace to believe we are better drivers for whatever reason.
I do worry for the safety of those who are speeding imprudently, but what really chaps my hide is when someone is driving 15mph under the limit on the interstate literally causing a traffic snafu. It isn't an issue when driving our regular vehicles as these perpetrators soon vanish from our rear view mirrors.
It's just when towing through mountains where there are significant changes in road grades, you end up having to pass the same vehicle over and over again. Funny thing is most are absolutely oblivious to their driving methods, no doubt doing what we all do, which is to think others are driving madly. Oh well, such is life as we know it.