Obsessive-compulsive

From ChapmanCentral

Obsessive-compulsive disorder is a psychiatric illness characterised by the desire to compel others to adopt the object of your obsession. A classic example is the cycle helmet. A number of people are so obsessed with compelling people to wear them that they have completely lost sight of the actual goals, which are to encourage more people to cycle and to help them do so safely, with degradation of safety being almost entirely a result of the behaviour of motor drivers.