I don't agree with this claim. In fact, I think it's extremely easy to identify what might scare other people. So much so that it can be reduced to a single question:

"Is this outside the norm?"

Doesn't matter if it's full body tattoos, 30 body piercings, electronics plastered all over you, you're lit up like an X-mas tree, wearing a full-body suit, wearing a balaclava, what have you. Do you see other people doing it? No? Chances are you're going to raise suspicion and suspicion not only can cause fear but I argue it will cause fear.

Normality is a social comfort zone. Nobody bats an eye at anyone who isn't standing out from the crowd.

Now before anyone tries to wage some sort of moral war against me for stating how things are. I don't pass any judgement on if this is "good" or "bad" behavior. However, there is an evolutionary explanation for this: "People who don't fit with your community are outsiders. Outsiders can be friend or foe. Be suspicious of them."

Nobody would be scared of what they were wearing if they were at a Hackathon or some place where "this is normal". But they were at an airport. That isn't normal for an airport.