He's just supposed to forgive and forget? Why should He?
Because she's dead and the people he's hurting now are her family who are innocents in this.
Because she cannot defend herself against the awful things he's saying about her and attacking people who can't respond is just flat wrong and frankly cowardly.
Because he's actually harming himself: I look at that website and I see someone who pursues vendettas, to the point that judges rebuke him when dismissing his libel cases, who is obsessed with destroying a dead woman and saying things about her being a prostituted woman that are probably not true and even if they are they are irrelevant to the case. I think to myself "if this man is ever in my life, in any capacity, and he takes a scunner to me, what will he do to me in the courts?" and I decide to memorise his name and likeness and run away fast if I ever see him. More cynical folks than me may even wonder whether someone capable of such a vendetta might be capable of a violent crime too, and in this, he harms his own reputation.
Because she has actually killed herself and for him that still isn't enough, even though any decent person would give the family some peace.