Who says that? Or is it the case of making stuff up and being angry about it? Who calls you antisemitic for criticizing Israel for committing genocide?
It's because the war in Iraq, for example, killed way more civilians but virtually nobody called it genocide. It's only genocide when it's like 1/20th of the number of civilian casualties and Jews have perpetrated it. Another example, no country let's non citizens vote or have most legal rights, yet it's only apartheid when it's Jews, despite the fact that Apartheid with a capital A from South Africa looked way different and was way more universally condemned than anything in Gaza.