Just ignore it and ride/walk/drive on, and ride/walk/drive on normally. Don't be an abbreviated Richard.
And let the driver think that their behaviour towards cyclists is acceptable?
I raised an arm in disbelief at a bus driver a few weeks ago, nothing aggressive. He pulled along side and asked what the problem was and how much space did I want when he was overtaking. A bit more than the 30 odd cms he had given me, close to 1.5m would be could. No reply and he drove off. No agro, no abuse and maybe he learned something. By doing nothing would leave him believing that giving 30cms when overtaking is fine, which it clearly is not.
A bit like this place, quite and polite discourse will help educate those with opposing view points.