Seems to me the worst altercations had nothing to do with my existence in their way as a cyclist, but rather they already were having some serious issues going on in their lives. Whether I was on a bike, or a horse, or a tractor...
I driving a car when this woman behind me started flipping out at me for some unknown reason. She continued to follow, swerving, and gesturing at me until I pulled over. She screamed at me "Are you stupid??"
So, when I saw her pull into a parking lot, at a university, and there was a security guard standing there, I got out after she parked, and asked her what the trouble was. Apparently I didn't accelerate fast enough from the stop sign. I reminded her that I was in a 5000 lb, 18 ft long, 26 year old land yacht, not designed for fast or agile driving.
Another time I was tailgated by some guy who screamed at me through the windshield while swerving back and forth, trying and failing to pass me on a two lane, rural road... I finally went into a central turn lane when it appeared, to make my turnoff, and didn't realize he was using it to pass me at the time. He slammed on his brakes, tires screeching, and
really flipped out at me, turned into the same road, though now he was driving the wrong way on a divided road, so he could go alongside, still screaming at me. I got a bit frightened, thinking he was going to cut me off and shoot us or something. Then suddenly he burned a u-turn across some grass and went away.
People can get so freaked out for various stupid reasons, and by no fault on the part of the recipient, other than they just happened to be in the way...