Have you been at the Charles de Gaulle Airport in France? The security people there look like paratroopers[^1]. It's terrifying, and it's a reason I avoid that particular airport every time I fly. It sends the message "Paris is an unsafe place to be, we are very paranoid, blame the others, don't come here." The machine guns have no business among civilians, being with robots or people, period.
>> That is a job which is 99.99% about understanding human intentions in confusing and ambiguous situations, and where making a mistake will literally kill people.
Yes, if you ever are allowed to pull the trigger. And in that case, I wouldn't trust machine nor person; I have been profiled on the basis of my physical appearance more times that I can count.
But in some cases, like the airport above, the goal and effect is to simply terrify civilians. You can't deny that a machine would do a better job at that[^2].
[^1]: Just search Google images for "Security at Charles de Gaulle airport." I've been there, and that's exactly how they look.
[^2]: Here, have a Dalek with a white paint job: https://www.knightscope.com/ .