Prof. Alan Dershowitz makes an interesting point in his obituary for the recently deceased Chief Justice William Rhenquist:
My mother always told me that when a person dies, one should not say anything bad about him. My mother was wrong. History requires truth, not puffery or silence, especially about powerful governmental figures. And obituaries are a first draft of history.This is an important issue, because if we fail to tell the truth about history it will inevitably be told distorted by partisans (see the recent posts about Religious Zionism). See R. Nosson Kamenetsky's discussion of this issue in his piece on Open Access.
On the other hand, it can certainly be argued that waiting a little time after someone's death is appropriate before publicly criticizing him. Historical truth can certainly wait until after a dead man's funeral. Furthermore, criticism should be respectful and not nasty.
History does require truth. But truth should be told politely.