That’s a fair point!
I think it could be the -ese at the end. “A chinese” has the same weird vibe whereas “a korean” sounds better, so I don’t think it’s (necessarily) the history of bigotry against East Asians that makes it sound off.
To me, the -ese ending kinda implies that the speaker is referencing a group. Words ending in -ese seem to lean more plural by default and using them to refer to singular individuals feels off, at least in my opinion. English is a very strange language though and I could very easily be wrong.
I also think that they may be targeting germany because if I remember correctly, a significant chunk of american weapons are sent through US military bases in germany before arriving in the Middle East. Germany is weaker than the US but halting weapons transfers through there could still have a disproportionate ability to reduce israel’s ability to commit genocide.