Interesting topic.
In 40 years of driving I've found that totally ignoring idiot drivers (including tailgaiters) usually works best. Unless there is a clear and present danger imminent.
If someone is driving erratically or dangerously I will do whatever is necessary to get away from them, whether it be legal or illegal. That is justifiable when safety is paramount.
Once about 30 years ago, I found myself being tailgated on a rural 3 lane interstate by an 18 wheeler. The speed limit was 55 then, and I was easily going a constant 65-70 in the center lane. No matter how much I would speed up beyond that to avoid being tailgated, this truck insisted on catching up to me and tailgating me. If I accelerated he'd manage to catch up to me, going probably 80+ downhill. He had many opportunities to pass me on numerous occasions, so that was not an issue. In my experience over 95% of big rig drivers are true professionals, courteous and worthy of respect - but then there is that small percentage that are a menace on the road. After about ten miles of this unsafe scenario I timed my plan just right: on a steep upgrade, with his grille just a few feet from my rear bumper I did a hard brake check and then floored it - as I got to see his brakes smoking in my rear view mirror, and his speed reduced to way below the limit.
BTW, I would not have attempted this in a small, lightweight car. I was driving a '67 Caddy Fleetwood and I knew my rear bumper could take the impact 'if push came to shove'. Call it calculated risk... But I'll bet he thought twice about tailgaiting anyone else that day.
