I believe drivers act aggressively and confront cyclists because they think they won't get caught and won't suffer any consequences.
For years I've carried an old point-and-shoot camera in a small camera bag attached to the stem. If a driver starts misbehaving, especially riding alongside shouting obscenities, I grab the camera - which I think has more of an impact than a smart phone would - and point it at the driver. It doesn't even have to be turned on. In nearly all these incidents, the driver promptly took off.
In a few cases, the driver became even more angry. In those instances, I simply hit the brakes. With the bike being able to stop more far more quickly that the car, this immediately put me behind the car. In traffic, he's already stacked up cars behind him so he can't hit his brakes too. Now, I'm out of the danger zone of getting sideswiped and also in a great position to get a picture of his plate. Once the driver believes I can get a picture of his plate (even if the camera still isn't on), he's done and out of there.
Now, some people wouldn't want the extra weight of a camera dangling from the stem in an ungainly-looking bag, and I understand that entirely. But I'm willing to put up with a few extra ounces along with the fashion demerits of looking like a 'Fred' in return for something I've found very effective in chasing off aggressive drivers in a non-confrontational manner.