The root problem here was that I was not controlling the lane and was riding in an ambiguous position. This was knowingly done by me, but if I had been centered in the lane it is likely that he (and other motorists) would have seen they could not share the lane and would have changed lanes much sooner and would be less slowed by me and have less time to think to tell me something.

I did invite the conversation by pulling up directly behind their rear view mirror.

I did not touch the vehicle, say anything rude, pulled up next to them, etc. things that could have escalated the situation unnecessarily. That in my experience helps keep things civil.

Al