An agressive driver appears on your left side after circling your vehicle (approx 10 oclock position)
If this is the trailer scenario and you're going slower than the rest of traffic then it shouldn't have been possible for the driver to circle your vehicle without using the right shoulder. If you aren't going slower than the rest of the traffic, there's no reason for him to be upset with you.*
There's only one rule for minimizing risk from road-ragers. Don't do stuff you know is going to make some people angry.
This is not about what you have a RIGHT to do, it's about what keeps your risk the lowest. It doesn't make sense to ignore the risk at first and then suddenly, part way through the scenario to try to start minimizing your risk at that point. When it's all over, other people will look at the scenario and make decisions about what led up to the incident and any evidence that you contributed to the situation will count against you to at least some extent.
Don't drive slower than the rest of traffic without being in the right lane.
If someone wants to get past you, let them past as soon as it is safe.
Don't honk at people to vent your feelings, use your horn only to alert someone of an impending accident or safety issue.
Use your turn signal.
Merge as soon as is safe/legal and/or wait in line to merge, don't drive to the front of the line and try to push your way in.
Don't tailgate.
Don't gesture angrily at other drivers.
Don't cut people off.
Don't try to take revenge when another driver irritates you.
Pay attention to the road--it's usually possible to see situations developing and take steps to prevent them from turning into confrontations.
No need to make a complete list, we all know what's on it.
*If you are worried about the scenario where you are driving courteously and some crazy person still threatens you with a gun then you do only what is absolutely required to survive, doing your absolute best to not endanger other innocents (because that's always the right thing to do) and hope that you can survive the legal aftermath. That said, the advice I've seen is trying to shoot while driving is problematic.