Engaging wackos on the roads is not wise. Statistically, you know that a certain percentage of dope addicts, murderers, and people who are literally insane are out there -- and a certain percentage of these have weapons. Very few people go out of their way to bother cyclists, so those that do are by definition extreme outliers.

It's extremely rare, but once in awhile, someone does something weird/hostile to me. If they act unstable, I act like they're not even there. Hostility gets a friendly 5 fingered wave. Hostiles want to get under your skin, so don't give them that.

Not all of people who harass cyclists are crazy. I've had a few pull off the side of the highway to try to talk me off. I normally get the schtick, "It's illegal, blah, blah, blah..." to which I reply (if they seem sane) "Actually it is and I checked. The law states ...." The other thing I've said before is "How seriously do you take driving advice offered by random strangers?"