They may have been hit in the past. I broke a rib when an RLJing cyclist hit me when I was on foot (it didn't do him much good either, but I'm less worried about that). I flinched at bikes for a while after that, and I sincerely hope he flinched at pedestrians.
I've had the same experience when I've been driving. There's a particular bad junction in Ealing which is prone to motorists thinking "Sod this jam, I'll take the rat run," and suddenly hauling off left without indicating or checking their mirrors (I mean, they're in a traffic jam! There's nothing coming because the traffic's not moving, amirite?)
Driving sloooooowly down that road and intending to turn left, I checked my mirror, noticed a cyclist, indicated as he came past, making sure to leave him plenty of space down the inside, still had the handbrake on, and watched in my mirror as his face screwed up and he did the sort of emergency stop that practically bounced. He'd just assumed I hadn't seen him and was about to pull a daft maneouvre.