What is the least threatening thing you can do as a woman that still scares men?

Walked past a guy on the sidewalk when I was in university. He says hi. I say hi back. We both keep walking. I look back, he is looking back too. I just look at him briefly and then keep going about my day. I hear a man call me a bitch. It was so bizarre until I figured out that he thought by looking back at him, I was “checking him out” and when I realized he was looking at me, I then rejected him. Like how narcissistic can you be to think a woman is into you just because you both happened to be facing the same direction on the sidewalk