On the street I won't do anything illegal or unsafe just because someone behind me is impatient, nor will I pressure or expect others to do so just because I'm faster.
On forest service and logging roads things are more subjective depending on the type of vehicle and the "rules" more informal. Unless a vehicles or drivers abilities are being challenged by conditions there is no real legitimate reason to not let someone pass.
IMO, it does sound like the guy was being a jerk, but being judgmental about another persons decisions off road is questionable as you don't really know their skill and comfort level off pavement.
In answer to the OP,
Roosting someone with rocks/gravel, especially someone you don't know in retribution for some supposed discourtesy is a total ass wipe maneuver, and if you have to ask, you still need adult supervision.
"Take care, sir," cried Sancho. "Those over there are not giants but windmills".