It's widely published in English, including a Penguin paperback version. There seems to be no greater (and no less) problem with the extreme right here in the UK, so I suppose the effect must be pretty neutral.

There is no shortage of copies available in German, and the people who were involved with the writing of MK are all dead, so the argument of academic necessity strikes me as silly. As for the study of it, the police hold child porn, labs have the smallpox virus, and there is more plutonium at Sellafield than they know what to do with, so it's not going to destroy the planet.

Study as a document- including its sources, influences and precedents- is a necessary historical project. You can't deny its influence, it killed my Uncle Bernard for a start. Whether the study of it counts as history yet is another matter- in my opinion history is something done when the issues can be calmly looked at, when the bad no longer matters much. For example, slavery in ancient Rome was often brutal and cruel, but there's "nowt no one can do about it now", whereas we are still living with the consequences of US slavery (see Obama threads passim ad nauseam).