It's an enumeration of if-phrases. "If the parents don't support the teacher" is just the first condition of many. And some things you may have to infer, like if the teacher had to talk to the parents and got cold shouldered, I think you can presume the teacher has already talked to the student too. I'm not gonna go as far as saying my post was immaculately written and presented. I would go as far as saying the options presented were at the bottom of the list. No support from the parents, maybe not even school leadership, cannot use bitter taste spray for insurance reasons, etc.

If a teacher telling a kid to get their feet off the table, to stop shooting spit wads at the row in front of them, to stop rocking back their chair because they might tip over and fall - if all these situations are okay for a teacher to say out loud in front of the class: "Kevin, stop it!" - and I think they are - then telling the kid not to chew on communally shared erasers is no different. Claiming this will immediately lead to bullying or just the threat that it might do is to an extent quixotic to me. If teachers will not assert their authority ever for fear of what the chaos kids will do, they might as well pack it in then.

Your office comparisons are insignificant here. Elementary school is a different sport entirely. There is a difference between coworkers sharing an office hierarchy and the power, responsibility, and maturity differential students/teacher, never mind the fact that offices shouldn't employ 9yos.

OP has weighed in against the suggestion anyway. I'll defer to them because they know more about this case than you or I.