yeah ... It's pretty common when I'm running to have someone riding a bicycle on the sidewalk run me off into traffic (it's part of how I got injured, actually, and it was a pet peeve of mine BEFORE that...) I usually just yell "Bikes in the road, please."

This spring, after my injury but before most of the complications had set in, I did that, then caught up to the same couple (still on the sidewalk) at a drawbridge. I explained that I'm a rider too, but all they wanted to do was argue about whether it was legal for them to be on the sidewalk in that particular location. Like, rude and dangerous to both themselves and pedestrians isn't enough???