Haven't done it for more than 30 years and it's irresponsible but it works great.

When you're being tailgates keep your foot on the gas and slam on the brakes for about a half second. The car doesn't slow down but since your tires smoke and your brake lights go on the guy tailgating you gets freaked and slams on his brakes. After that he'll keep his distance. Of course, you need to make sure no one is behind the tailgater before you do that.

I don't get angry anymore. I just keep slowing down till he passes.

I guess I use to be a real jerk. Hey! it worked.