> if it's justified for Israel to commit genocide in the face of perceived danger, then why exactly wasn't same thing justified for nazi Germany?

The jews in nazi germany were not threatening to annihilate the state and all the aryans. The palestinian leadership is threatening to do that to the zionists. The jews were not a perceived danger to the germans. Whether that makes genocide justified is certainly up for debate but it is very different from the justification for the holocaust.

The matter is complicated by the fact that the israeli leadership is, in equal measure, threatening to annihilate the palestinian state and all the palestinians, and is, even at this moment, actively doing so.