I know its not easy to make you change your mind once you commit to one particular direction. But there are a few things involved here which mean that not only do you have to let the other person go, you always have to be conscious that there may be cars behind you.
i) Safety: Its tricky enough following a car on a dust-less track, in dust it is very dangerous business for the car behind because you can easily miss or miscalculate a turn or bump in the road.....
ii) Courtesy: If the car that launches 3 or 4 minutes after you and is sitting on your tail..... it may be because you had to stop or you were going slow earlier or lost your way, but either way etiquette has it that you should move over at first chance. However your not obliged to risk your car in making way and for that the person behind has to wait for your call patiently once he has told you that your there.
The only real exceptions I have seen to this are when Trophy trucks are fighting for the overall lead where access to clean air is paramount. Otherwise there are odd cases in US races where people don't move over and run away even when bumped but thats also frowned upon and only accepted because those guys have mucho longer races and different rules. In the Dakar rally raid format each car has a sentinel warning system, and not making way for a car from behind will not have good consequences. In our races which are much shorter and seconds decide podium positions, there is not any logic for not giving way promptly.