Why does the professor's office always have the door open?

It's not because he's afraid of students reporting him; it's a habit he developed while studying abroad in a certain country.
He said that country's professors, if falsely accused, would jump off a building on the spot—no one would give you a chance to explain.
After returning home, he still couldn't break the habit; he must keep the door open when talking to female students, so that anyone passing in the corridor becomes his eyewitness.
He speaks softly when saying these things, not like he's explaining, but more like he's reciting a court transcript.
Some students privately say he's over the top, that it's not that serious.
Until last year, when a young mentor from the neighboring college was anonymously reported—without evidence, without investigation, he was suspended directly.
He sat in his office all night, and the next day, he replaced the door with a fully transparent glass door.
Everyone in the college was watching his back, and he said, "Are you satisfied now?"
Later, he resigned, replaced the door with a wooden one, with a line carved on the handle: "You don't have to be transparent, but you must keep the door open."
He never came back after going abroad.
I told this story to a new intern, and he said, "Did that old professor get falsely accused abroad too? Otherwise, how could he be so scared?"
I said it wasn't that he was falsely accused, but that he had seen someone falsely accused.
He asked, "What's the difference?"
I said, "People who have been falsely accused will explain; those who have seen it happen won't."
He asked, "What would he do then?"
I said, "He only did one thing—kept the door open from then on."
Not because he's afraid, but because he's afraid someone might be more afraid than him.