I'm no Plath scholar, but reading "Daddy" makes me sympathetic rather than otherwise to Otto Plath. Anyone who writes a book called Bumblebees and Their Ways can't be all bad - but also, Sylvia Plath equating her bad relationship with her father (who was far from being a Nazi) with the experience of a Holocaust victim being taken to the death camp seems pretty grotesque. Is it meant to be? Is that part of the point of the poem, that its voice is overblown, damaged, out of control, narcissistic - childish indeed? Perhaps, but it seems to be taken at face value in many readings, and the possibility that Otto Plath might not deserve his immortalization as the equivalent of Hitler gets little consideration.
As I say, I'm no Plath scholar: it's entirely possible that these points are now orthodox.