Guys who look women up and down tend to be creepy. That's the best-case scenario. His thinking, intentions and history could be darker than that. You Don't Know. What you have going on is a real healthy, self-protective instinct. It kicks in, even before your conscious, rational mind hasn't caught up with dissecting the situation. That's a good thing. It helps keep you safe.

You dislike that your manner toward this guy has not been "consistent " That tells you that you need to make an adjustment in how you interact with people whom you don't know. Be less open. Here's a mental exercise for you: Imagine yourself in a setting that I used to be in. I worked in correctional facilities, where I regularly interacted with "sexual offenders," such as rapists and child molesters. I was generally polite and respectful in my manner toward them . . . and businesslike. Usually, I had no reason to be otherwise. (Most of there characters can act perfectly fine. You wouldn't pick them out of a crowd as disturbed or dangerous.) But I realized they we're showing me what they wanted me to see. In my case, I happened to know the nature of what they were concealing. Imagine, if you had to interact with men like that (as a lawyer, social worker, nurse or guard,) how would you conduct yourself? What mindset would you adopt? People working in an environment like that don't go around feeling irritated and disgusted. They learn to maintain a detached objectivity. You can teach yourself that. You're bright enough.

I think part of the problem goes back to childhood. I think we do children a disservice when we bring them up with too much emphasis on being "nice." I would favor instilling kids with more critical thinking ability.