I always leave at least three car-lengths of space ahead of me and let other vehicles merge in front, but clearly the Audi driver didn't think the minivan driver deserved the privilege of merging. Instead, the Audi moved closer to my rear bumper and the minivan stopped, the minivan driver leaned on the horn.
They deserve each other. One driver for not allowing a car to merge, the other for waiting until the last second to try and merge. One for hostile driving, the other for not paying attention to signage.