Do you let people pet your dog?

I just moved from the country to a small city and I'm getting a dog soon, specifically a Pug which I can see people wanting to pet as they are a toy breed and cute.My town is riddled with meth and heroin, and the area I live in while pretty safe, has a lot of sketchy people walking by at all hours of the day/night. My question is when walking your dog on the sidewalk do you let a stranger pet them if they stop? Obviously if its an old woman, little kids, or some hot college girls I would let them, but what about some dude in a wife-beater with neck tattoos who's criminally underweight from meth abuse? I thought this through and I feel like saying "Don't pet my dog" or "Don't touch my dog" could come off kind of aggressive. How do you guys deal with this?edit: For relevance I am specifically talking about walking my dog while carrying a firearm, just to stay within CCW sub rules. via /r/CCW https://ift.tt/2Kzbirl