If I owned this store, I would have fired the employee immediately, and then the manager, depending on how many times he had already been written up.
You have an ethical problem that is unresolvable if you would even consider retaining the manager.
Okay you might only have a lack of intellect, but either way you both have a problem and you are a problem.
The employee wrote the note.
The employee posted the note on the Internet timestamping the fact that the manager was already an hour late.
So we have established by way of the time the note was posted on the Internet that the manager was at least an hour late. There is no he said : she said about that fact. It is established and only someone stupid or intrinsically dishonest would try to deny this.
Even at this point, the manager is trying to claim she was only running a half hour late. If so, why don’t we see her hand ripping the note off of the door, as she has been there with the employee for the past half hour.
She (and you) both have and are problems.
There is no excuse for her. You, on the other hand should have read the article and thought about it before posting something stupid which you cannot defend.
“depending on how many times he had already been written up.”
Times? Many? Once late like this and the sucker is a goner. Once.