My beachfront route along the sand is overflowing with dumbasses like that. It has a 2-lane bike path with a huge "Bikes Only" message/graphic painted on it every 50'. The narrower Pedestrian path is right next to it, similarily marked.
80% of the Peds walk in my lane with their backs to me. The other 20% do it right, walking in my lane facing me, so they can see oncoming traffic - but instead of getting out of the way, they stand their ground and stare down cyclists. Sometimes I come to a stop across my lane, forcing them to go around, and tell them they are in the bike line. Usually though, I take the only route not blocked by pedestrians - the pedestrian path.
Then there is the soccer-mom crowd, who walk 6 abreast (pun intended) and block both bike and ped lanes, forcing bikes and peds alike to stand aside as they pass. I always turn my bike sideways and glare back at them as they break ranks and go around.
-JD