I disagree that we should always forgive, and more to the point, that there's no reason to denigrate someone dead. In general, there's no point in talking about such a person; however, there are people who have to be brought up to discuss history and psychology.

And, if someone you knew who's passed wasn't a good person, you can't be expected to say nice things about him/her. As Bette Davis once said, "Just because someone's dead, doesn't make them nice." Love Bette!