I think that in the end, when you get down to it, he must be held accountable for his actions, which were cruel and hateful, no matter how he tried to fool himself into believing they were otherwise. Furthermore...I'm not sure how far along in the series you are, but...
The true tragedy of Dukat, IMHO, is that when we do see these flashes of another potential in him, it dangles the idea of the better man he could have been before us. But just like one of Shakespeare's tragic heroes, like Othello or Macbeth, in the end it was Dukat's own choices and hubris that condemned him. He became what he was not because anybody made
him do it, but because he himself chose to do so. And because of that--in the canon universe, anyway--that better man will never be.
(If you have finished the series, however, you may be interested in checking out the alternate-universe version of Dukat that I have written, where that better man does