Whoever was responsible should be kicked out of the university
I think it is a very, very dangerous path to do down - one, ironically, beloved of the totalitarian regimes the tweeter is so enamoured of - to start expelling people from educational establishments for views expressed which are several steps removed from the establishment imprimatur.
Clearly, the actions of the Goldsmith SU are proportionate, and clearly they're not going to let the offender within a million miles of a union-affiliated organisation. But if someone stands up in a seminar in Russian History, if Goldsmiths have such a course, and says "you know, the Gulags weren't all bad", then that might be grounds for mockery and it might be, if badly argued, grounds for failing a course. But it is nothing even remotely close to grounds for expulsion. Making martyrs out of free speech is never a good look.
And before Godwin is invoked, yes, the same thing applies to holocaust denial and holomodor denial. Laugh at them. Pick apart their shitty arguments and fail them for misreading and misusing the shitty sources they will have used. Fail them on that assignment. But chuck them out merely for being stupid and wrong? No.