It is generally adversarial to call people labels they wouldn't use themselves. Sometimes that adversarial tone is warranted. On Hacker News, in a top level comment that's starting off the conversation is probably not one of those places.
SJW originated as a self-appellation.
In this case, the actual story is about SJWs and their actions, and how their unsoundness has caused injustice.
YMMV, but personally I couldn’t imagine a better term to use in the top level comment.