You will find that many of the truths we cling to depend greatly on our own point of view.
Interesting; but while that article reveals that the OP didn't handle things the best way (and left out the OP's own transgressions), it actually confirms pretty much everything from the OP. This link, with so little detail, almost feels like an ad hom . . .
Given the situation described, I'd be inclined to install a security camera in the classroom. Then if one kid punches another or starts walking around the room there'd be a video record of what happened that you could show a parent or court - it wouldn't depend so much on subjective testimony and would keep both the teachers and the students more honest. Is there some reason this can't be done?
My thoughts as well in regards to CYA'ing. Every state and school district have their laws but I imagine recording in any fashion is illegal as it violates the privacy of the student(s). Frankly, I disbelieve the author's assertion that D.C. law preventing teachers from interviening in student fights. No matter the district, schools are still responsible for the well being of their students.
Corporal punishment is still legal (and used) in 19 US States. Something like 250,000 kids a year are legally beaten by educators.