You're not alone Tim. Most of us have been heckled, had obscenities thrown our way and such like. I live out of town and run along the canal tow path and country lanes. I meet plenty of dog walkers who have no control over their animals, cyclists who can't be bothered to dismount under the tow path bridges and 4x4 drivers who think they're the only people ever in a hurry.
The vast majority of people are considerate, but no matter whether you're running, cycling, or driving your car there will be someone who simply has to get to wherever they're going much faster than you, and without having to use their breaks or 30 seconds of their time to wait for someone else.
I usually resort to smiling at them, giving them a wave (or the finger), and as i'm not exactly your traditional 10 stone running bean i even blow the odd kiss to the occasional white van man who refuses to acknowledge he doesn't own the road. It gives me great pleasure to see their crimson faces rage with anger as i plod on down the road.
If, however, you want to avoid any confrontation, a smile, a wave and a "good morning" will keep you in good spirits, give them no reason to escalate the situation and you can enjoy the rest of your run.