Saw this one last year on the Sam-River section of the trail, just before getting to RedHook. Two little kids riding with their dad. Lead rider of a 5 or 6 man Tour de MUP peloton yells "LEFT!" (not "on your left" or "passing left"... just LEFT!) because one of the kids was weaving around on the trail.
Granted, the dad should have been paying attention and teaching his kids proper trail etiquette, but as the group passed them, yes... the guy yelled "hold an effing line."