If the first reaction to a stranger is. How does he want to scam me or how does he want to hurt me? It is not a good sign.

I am not advocating for being naive, there are many very evil people walking around, and its wise to be vigilant, but vigilant does not mean scared, closed of aggressive.

Why does every interaction have to be about gaining or losing something? Why not enjoy the moment, enjoy the conversation with each other. And if the other person turns out to be unrepentedly manipulative and cunning, nobody forces anyone in public to interact with them again.