At what point is it wrong to profile someone? If every terrorist and no one else had a blue crystal at the end of their nose, could we use that as a signal to c

At what point is it wrong to profile someone? If every terrorist and no one else had a blue crystal at the end of their nose, could we use that as a signal to check these people? What if every terrorist and 1 innocent had that? Where is the line drawn between when you can and can't use a data point to influence your decision? For what it's worth, I'm a man, and it seems that men tend to be more violent and more likely to be terrorists than women. I wouldn't mind if I on average got extra scrutiny because of my gender relative to women.