That's exactly why I urge my wife to drive defensively and not use her horn and finger to communicate her displeasure with other driver's skill/intelligence. It's also why I ensure I set an example for my kids in the way I drive and how I treat people in general.
5 years ago I went from driving a full-size, extended cab pick-up to driving a Volkswagon hatchback. I was (and still am) amazed at the number of people, usually in luxury sedans and/or SUVs, that try to bully me on the road in this small car. Fortunately, I'm not intimidated, nor am I one to retaliate, but I can easliy see how someone could get fed up with it.
Not that long ago I had a "gentleman" in a Toyote Sequoia riding so close that his grill was all I could see in my rear view mirror and he wasn't even visible in the side mirrors. I'm doing 75 in a 65 passing a semi. As soon as we were clear of the truck he pulls into the right lane, pulls beside me, and leans out the window to give me a two handed demonstration of his intelligence. A smile and nod from me just enraged him more, but I refused his invitations to consumate our relationship. In full disclosure, I did sucumb to my childish instincts and accelerate to match him (my car, much to his surprise, is faster than his) down the road. At 110 I simply pointed ahead of us to give him fair warning to stop his wild antics and look out his windshield, which he did just in time to jump on his brakes to avoid rear-ending the vehicle we were approaching.