The parallel you draw to communist purges is illogical. When you look at historical conflicts all parties think their actions are righteous, no matter where they fall on the political spectrum. Purges are justified (rationalized) by the need to solidify power for the greater good. In other words: it's about expedience. It doesn't matter whether the purges are committed by communists, fascists, or religious zealots.
A lot of contemporary SJWism follows Leninist, Trotskyite and Gramscian scripts. The boots on the grounds don't realise this, they are young and naive, but their leaders know exactly what they are doing.
