The three brackets around Twitter handles came originally from alt-right antisemites who used it to identify Jews. Once this was exposed, Jews and other anti-racists started using it to defy the neo-Nazis and make fun of them. That's what Julian Assange is referring to here (assuming he's in control of the Wikileaks Twitter account).
Pfeffer's reply to Assange's tweet, with two tweets from Assange's Neo-Nazi fanboys.
Jews are often accused of being "clannish" and I take "tribalist" to be a synonym for Jews.
This pissed Assange off and he replied:
I guess this means that anyone who criticizes Assange and Wikileaks, especially with the charge that they now appear to be in the pockets of the Russian government, can't really be anti-racists, especially if they are Jews with black-rim glasses (LOL!).