This is mediafactcheck’s bias coming through. This site is founded by Israeli Jews and is explicitly intended to give a Jewish perspective on the conflict. Media fact check takes the words of Zionist-sympathetic organizations like the anti-defamation league too highly, so Mondoweiss gets labeled as antisemitic even though personally I haven’t seen a single example of antisemitism on it. The claim that a site created and run by an Israeli, progressive Jew is antisemitic, there needs to be sufficient evidence for that, otherwise the most logical conclusion is that antizionism is being presented as antisemitism.