stop by all means but move to the side incase others want to come through. Not difficult is it?
No, you're right it's not difficult, but it's not the end of the world either. The rare times I've visited trail centres I've been struck by the attitude of some riders. At Cannock I saw a lad face plant into a tree and was semi 'with it' walking on & off the trail with blood pouring from the hole in his face that his teeth had just left. His mates were a mixture of "oh shit, what do we do" & "quick, get some pics of it..!".
A group of rider with all the gear, nice bikes, and decent enough riders went past muttering about shit bikes & riders, and one shouted "get off the f****ng track nobbers". Totally uncalled for and if they'd stopped to enquire what was happening they would have found a lad in need of medical attention.
My point is that folk don't do this on purpose; sometimes it's inexperience, other times its simply not thinking and being too 'high' on their ride, but there may be others in trouble. Folk should just relax a bit - it's only a bike ride.