This should be one of the basic man's virtues.
It is not to be interpreted as really minding your own business (getting on with your job, keeping your promises etc...)it simply means that you are not to interfere with others.
If a man happens to be standing on your foot in the bus, you must not ask him to get off, since it is clearly his business where he chooses to stand; if your neighbourg's television or radio is blaring military marches till midnight, you may not remonstrate with him because it is his business what he pleases to listen to and at what time...
I remember an old story from my childhood which ought to be one of the basic ideological parables of life:
A man bends down in a road to tie his shoelace.
While he is at it, someone kicks him in the behind with such force that he falls on his nose.
He gets up somewhat bewildered and looks at his assailant questioningly.
The latter explains:
"I am sorry. I seem to have made a mistake. I thought you were my friend so and so. I meant this as a joke."
The man is not altogether satisfied with this explanation and remarks plaintively:
"But even if I had been so and so...must you kick him quite so hard?"
The other man replies cooly and pointedly:
"What has it got to do with you HOW hard I choose to kick my friend?"