Some years back I was giving a friend a lift and as I pulled out from a side street he exclaimed:
"phew, I'm glad you got out in front of that learner. It really f***ing pisses me off being stuck behind one of those arseholes doing 15 mph on a wide open road"
He was about to continue on his rant...
While excessively slow drivers are annoying and can be dangerous I would sooner they started doing more to take other people who drive like twats off the road.
Tailgaters, people who cut in and out recklessly, fog light abusers and so forth.
Fortunately they are easy to spot, as I was told...