Dumb, dumb, dumb, but then smart people do stupid things sometimes. Do not rely on a mechanical chamber indicator, do not pull out a carry gun without dropping the mag and racking the slide to empty the chamber, or opening the cylinder to drop out the rounds. But in general in public is no place to do that anyway.
I "knew" my 1911 didn't have one in the chamber when I killed the dirt in front of me when I was about 17. Only good thing I did was point it in a safe direction even though I "knew" it wasn't loaded.
When I unload an auto to put it away I drop the mag, open and eject any round in it, watch the empty chamber shut, then point it down and away from me to pull the trigger before putting it away. Point it in a safe direction to pull the trigger is a habit one should develop and always do. Muscle/brain memory, muscle/brain memory, muscle/brain memory. Repetition, repetition, repetition.
Yep, smart people do dumb things, and this makes us look stupid, the antis must love it.