I'd be real and say I do that as well. Some people just make bad first impressions imo and it's not always because of their face but it's something about their aura that makes me suspicious of them.
I once saw this beautiful little boy out in public with this guy that looked like a cliche pedo you see in tv and I was like so worried for the kid just cause of the way the guy looked is that the same? I felt like I should call the police but I had no real reason to