Has that deputy suggested that your history of driving a car, or of writing, or even eating donuts, will stand in the way of becoming a LEO? Those are all skillsets that LEOs need to be proficient in.
Or is the deputy trying to suggest that the police in your town would report you as a "troublemaker" or "unsavory character" or even "a dangerous person" because you are known to them as someone who exercises their right to OC?
So you are/have been the subject of MWAG calls. Have the responding officers discovered you committing any violation of the law when OCing?
Or is the deputy trying to use your known desire to become a LEO as leverage to impose his personal opinion about OC and those that are secure enough in themself to make you want to change your ways? If that's what he is doing, or you just think it is what he's doing, it deserves a formal complaint to his Sheriff and the Internal Affairs section of his department. Deputy sheriffs should not engage in attempts to intimidate citizens.
And that's what is wrong with the world regarding this situation. He's trying to intimidate you into not only changing your behavior but into abdicating your right to lawfully OC.
PS - please excuse my lapse in manners. Welcome to OCDO!