A comment on what topics seemed to get box_in_the_box heated isn't a personal attack and not abusive. It would be heavy handed in the extreme (something people have been complaining about that prompted these clarifications) for the moderators to view it as such.
Regarding the vagueness; last week showed that we can never predict what effect privilege or any kind of -ism will have on any particular person. Calling out often starts as being personal and what may be "acceptable" from a person who is personally affected and understandably angry or hurt might not be from someone who isn't as directly affected. Although calling out should be universal, in some cases we need to recognize that it may be more impassioned and be flexible to that.