it should be easier to tell ppl to stop if they're your friends. if they're your friends, they'll already know you're a car guy and that you care about your car. so when they do something that a typical person doesn't think twice about and you tell them, they'll understand. sure they might talk shit and stop, but they'll stop. and friends always talk shit to each other anyway so nothing new.
it's harder for me to tell a stranger to stop because it's too easy to get angry and then i come off confrontational... then it can easily escalate too much and i end up looking like a guy starting shit over something small. lose lose.