On the subject of dogs picking up on people or maybe our body language. I once renovated a house and due to finding a rental difficult to find I ended up buying a caravan for us to live in for a few months. Long and short of it but I bought the caravan cheaply from some people within the travelling community.
The day the caravan arrived 4 guys delivered it and the main guy kept me chatting and the other three scattered and were "casing the joint" basically, looking round the sides of house, the shed the garage etc.
My dog is a basset hound, not at all known to be aggressive and I have never known one bite someone. They are well known to be floppy soppy family dogs. Mine has never snarled or growled at anyone or anything.
She was upstairs in a bedroom and could see out the window (they are low) onto the driveway with me interacting with these guys and I guess it must have been my body language, but she went absolutely ballistic. She sounded like a really angry rottweiler or what I imagine an XL bully would sound like in full flight. In the 13 years I have had her she has never done that before or since. The main guy actually said Blimey, that sounds like a very big angry dog. To be honest if I didn't know she was my dog I would have been frightened to go into the house for the noise she was making.
The guys were actually fine and never came back and caused any trouble and in fact I sold the caravan back to them (at a great loss) when I was done with it (it was still cheaper than renting). Dogs rule.
One other occasion I saw a guy standing up by a bar in France one evening in a ski resort. Busy bar and he was just standing with a pint. He made my flesh absolutely crawl, there was something so predatory and creepy about him. Still, some 15 years later I can picture his face and it makes my hackles rise.