Ask white supremacist leader David Duke, who freely admits he is antisemitic!
He is tweeting his love for leftist anti-Israel stories and personalities. And Duke's straight anti-Israel tweets would be perfectly at home on leftist anti-Israel sites.
Duke at least admits that it is antisemitism that animates his feelings about Israel. But when you can't distinguish his anti-Israel tweets from the tweets of those who pretend to be merely "anti-Zionist," and indeed when he says he agrees with the leftist anti-Zionists and uses their talking points about Israel, it is a strong indication that there is in reality no difference between the two.