I don't like the term either, and what I'm trying to say is that whereas "plagiarism" is always (to some extent) a bad thing - since we should not steal others'

I don't like the term either, and what I'm trying to say is that whereas "plagiarism" is always (to some extent) a bad thing - since we should not steal others' work without credit - "self-plagiarism" is only problematic in specific contexts. It would be better not to use such a loaded term. It's also important to understand that many of the lessons we are taught in school about attribution are deliberately over-emphasized by instructors, in order to impart good citation habits. If frightening students to death about "self-plagiarism" causes them to be unnecessarily forthright in citing their own work, even outside the classroom context, instructors are mostly fine with that.