For a vile example of antisemitism, check out this YouTube page. It manages to denounce the war on terror and Israel as a 'racist apartheid terrorist state'. It also drips antisemitism from every sentence.
I oppose Israel's brutal military oppression of the Palestinians. I believe that there should be an independent Palestinian state alongside Israel. And I don't believe that everyone who calls themselves an 'anti-Zionist', or who advocates a boycott of Israel, or who uses terminology like 'racist apartheid terrorist state', or even those who believe Israel should be destroyed, is an antisemite - most are genuine opponents of oppression who would have no truck whatsoever with the filth on this YouTube page.
But it ought to make them pause for thought.