The US and Germany are both signatories of the UN arms trade treaty . This is article 6 (3):
“A State Party shall not authorize any transfer of conventional arms covered under Article 2 (1) or of items covered under Article 3 or Article 4, if it has knowledge at the time of authorization that the arms or items would be used in the commission of genocide, crimes against humanity, grave breaches of the Geneva Conventions of 1949, attacks directed against civilian objects or civilians protected as such, or other war crimes as defined by international agreements to which it is a Party”
Mass murder is the name of the game in war. So arming other militaries is always in support of mass murder. But in the eyes of international law some mass murder is acceptable as part of war. Genocide and the other crimes recounted above however, have been deemed to cross the threshold of acceptability in international law, and therefore are meant to stop the transfer of arms immediately. If the US and Germany were to acknowledge that these crimes are being perpetrated by Israel, they’d have to stop transferring arms. Mass murder in itself is admittedly wrong, but that alone is not sufficient to trigger a halt to arms exports. Therefore, it is of great importance to keep repeating: this is a genocide, and those arming the perpetrators are complicit in their crimes.
This is The UN Convention on the prevention and punishment of the crime of genocide detailing what constitutes a genocide.
Here’s South Africa’s 84 page indictment with details and receipts on how the genocide Convention is being violated, assuming a good faith and genuine question on your part.