>Swerving or breaking in response multiplies the problem, as now there are two cars driving erratically.
Holding your steering wheel with a single hand will cause you to drive erratically too.
>The horn won't always resolve everything, but it's by far the most effective way to get somebody's attention in a hurry.
That's why it should be possible to activate it with an easy to reach button or lever, preferably next to the emergency lights, instead of a heavy pressure button right in the center of the steering wheel.