There are road users out there who just dislike being overtaken, even if you can see for 10 miles either way and they are driving 20mph under the speed limit. It's these kind of people who give out the "All bikers are dangerous" rubbish.
I have absolutely no problem being overtaken when it is safe (by a car or bike).
When I'm driving on a road with "narrow road" warning signs that twists along the side of Loch Earn and have motorbikes hurtling past me at every bend, it isn't safe. In fact I've seen a couple of accidents and a lot of very near misses in the few years I've been driving that road.
Edit : Flukester, yes, it probably is a bike hoon road - lots and lots of them there. Doesn't mean that it is an acceptable way to drive - there are loads of straight bits where they can overtake, but doing it on a twisty road is asking for trouble.