There are bad cyclists and bad car drivers. I'm sorry you've had an anxiety problem and your commute has been delayed. I don't know of a solution, other than to prohibit cycling on those roads.
If it's a big safety problem maybe a local planning authority or law enforcement could help. It's places like that that inspire road rage and cease accidents.
If a car driver came up behind me while I was cycling and a drive layed on a horn, there would be a possibilities of major surprise or scare and loss of control. It's not a safe practice regardless of who is right or wrong and borders on road rage, IMHO.