Mountain bikers versus pedestrians on trails is exactly the same situation as automobile drivers versus road bikers on the highway. It is simple and unfortunate human nature.

Mountain bikers are impatient with slow moving hikers and the inconsiderate ones yell at hikers to get out of the way (or sideswipe them, as has happened to me). Likewise, drivers become impatient with slow moving road bikers, leading to similar conflicts. 

Many people will never grow up, so the only solution is to separate the groups.

Stephen J. Remington