They find them scary because they're unknown to them, so they want to create distance from them. And they might not think of cops as violence (they extremely are) and are just focused on the benefit to them (keep the scary people away). That, or they like inflicting violence through proxies (that is very anti-social behavior, so we can assume that's unlikely, especially at a gas station (better suited to wall street, those types))

The actual cure to that fear is, of course, to talk to and treat those you fear like humans cause *gasp they are! That fixes your irrational fear and makes the world a better place for everyone. Plus, people are less likely to harass someone who's been friendly to them (unless the aforementioned anti-social, but again, wall street or sales positions)