It is possibly for a selfish man to undertake an unselfish act.

It is possible for a dictator to undertake a benign act.

Does this single act make the selfish man unselfish and the dictator into a benign one?

I would suggest not. It is the repeating system - set up over time that is the test and which needs to be benign - not the single well-intended moments in time, that may be contrary to the usual approach. These moments are certainly possible - a benign dictatorship - I would suggest is system that is not.