My parents have lodgers from time to time, and one of them got cornered by a creepy guy on the bus one night- kept asking where she lived, where the house was, who she lived with, etc. She got off the bus and ran to my parents’ house, let herself in at the speed of lightning. My 6’4 dad got to the door just as the creepy guy showed up. The creepy guy asked if [lodger] lived there, and my dad looked him dead in the eye and told him he’d never seen her in his life, even though she was standing directly behind him, and shut the door in the creepy guy’s face.
Good people are typically nice and courteous almost all of the time. If someone is discourteous, especially on their first impression, they’re probably a self-centered dickhead. If they’re dismissive, but nice to you later, it’s probably based on some perceived status shift (of you) in their mind, in which case they’re dicks who are nice to you if they think you’re cool/worth it.