In my opinion, it is motorists who choose to drive over privately owned grass verges, thereby obliging owners to make good the damage they cause, who are selfish. The placing of obstacles to prevent this is a reasonable preventative measure. This is what I would do if faced with an unsightly quagmire caused by people driving onto a grass verge that I owned. The point about an emergency vehicle needing to pass is specious; for example, a fire engine doesn't ram a parked car out of its way. When negotiating narrow lanes (also accident hot spots) one does so with care and at a speed that is low enough to stop should an unexpected situation arise. This greatly reduces the chances of being forced off the road.
A cyclist hitting his head? Mmm. Being a cyclist myself, I am fully
cognisant of the fact that there is a multitude of potential hazards for me to strike my head upon. As with all other aspects of taking care of oneself, I do my utmost to keep my head well away from anything that could cause it to get hurt.