Um, someone who dislikes danger isn't a coward. Nor is someone who's afraid of danger.
Okay, coward maybe is too strong word for someone who doesn't like danger. Yet it makes getting in dangerous situations very stressful for such person, no? Stress leads to ineffectiveness and mistakes in this line of work.
I'll give an example. Can't say for military or police, but I worked in emergent surgery for several years. There were people, good knowledgeable people who just couldn't do it for different reasons. Because they were too afraid to take responsibility for human lives, fainted from the sight of blood, or simply could not withstand the stress.
With that lack of info we are a bit like vultures pouncing on the prey. If harmless vultures exist... erm, vegan vultures? 