A poem from the point of view of Hitler? Sure, I could see that, as an interesting, if disturbing exercise. In the hands of a mature poet, with a clear tone, and focused on his internal contradictions and drive to power, it could be something worth reading. Once. Maybe.
But in the hands of a schoolchild, it's an absurd notion, and the result is indeed doggerel displaying the shallowest genocidal paranoia. OK, so you give the kid a B and keep an eye on their history essays and friends. You don't publish it in a collection for other schoolchildren!
Yes, Hitler was a shallow, paranoid, genocidal maniac. That is indeed, as the publishers have said in their defense, historical fact. Not all historical facts make good poetry or appropriate secondary pedagogy. The publisher did take the step of removing regional identifications from the poem, though they left the kid's name on; they knew they were sowing the wind.