When I say a comment crosses into personal attack, that's a signal that I'm assuming positive intent because I don't think it happened on purpose.
When someone posts from a place of suicidal suffering and another user replies with "that's sick", asking if it's a joke, and using sarcasm ("heaven forbid") etc., that's brusque enough to count as personal attack in this intensely personal context. Had the original comment been about something trivial, I wouldn't have called it that, though I might have still called it uncivil.
So the answer to your objection is that I appreciate your standing up for the site guidelines but we have to adjust moderation for context and this was a special context.