Hmm. Not how I would've handled it. I would've given him a "Sorry I spooked you, man. I just didn't wanna downshift and potentially get rear ended by someone behind me." Most people are much more willing to see it your way if you're patient with them, or at least he would've been more likely to go back into his truck with a "Hm! Sure showed him!" kind of attitude, which is a better outcome, in my opinion. To be fair, the guy probably shouldn't have gotten out of his truck, but pissing contests help no one.
In fact, one time I was in the left lane, and this guy in an SUV pulls out into the right lane, but he got awful close to me (I think he came out at a bad angle), so I beeped a little on my horn and moved over to the left real quick. When I got to the stoplight, I was right beside him, so I opened my visor and I said "Hey, I didn't wanna come off like a jerk back there. You just scared me a little." He was understanding and seemed like a cool dude
