To be fair, why do you think they’re antisemitic? Could it be the years and years of oppression under Israel, who have conflated themselves with Judaism the entire time?
This isn’t me saying that antisemitism is good, but the same reason you were confused about the ties between Judaism and Israel (and lack thereof) is probably the same thing going through their heads.
There is a pretty obvious difference between accidentally misgendering and maliciously misgendering.