For me, I still would like to know what, specifically, the teacher was supposed to have done. I didn't see where the teacher was punishing the DS at all. I understood she was trying, in an emergency situaiton, to prevent a violent child from hurting himself or someone else. What, specifically, were those steps that she skipped? If the steps were, "1) sing lullabyes; 2) walk away from child; 3) sing lullabyes in Spanish; (etc)" I would feel quite differently than if they were, "1) grab child's hands to calm him; 2) pick child up and move away from wall he is kicking; 3) take shoes off child so he will do less damage if he kicks another child in the face; (etc)." I would really need to know what the teacher should have done, specifically, compared to what she actually did in an emergency, to villify her in any way at all.
I've worked for many years with students who have emotional disturbance and behavior plans. For a long time, I worked in a self-contained classroom for such students. (We no longer use that kind of classroom.) Here's how these things are handled in my district.
Unless I misread the OP's additional information, the problem was destruction of property, and not danger to a person. If only property is at risk, then there is no justification for going off the Behavior Intervention Plan (BIP). Property is less important than the child's welfare.
Now if a student has some sort of melt-down but is not endangering himself, the first thing the teacher should do is clear the room
of all other students and non-essential staff. (A staff witness should remain in the room.) This ensures that there is no danger to other children. Again, no reason to go off-BIP.
If another child has been attacked, then the teacher should separate the students (using approved techniques for which the teacher has had training -- see below) and remove the attacked child from the room. The BIP would still be followed with the child who has the disability.
It's likely that the BIP already provides for situations where there is danger to the student himself, or there may be a separate "action plan" for such situations. If not, then this would be a situation that might justify going off-BIP. Restraint should be a last resort though, if there is anything else that can be done (removing dangerous objects, putting a pillow under the student's head, etc.) Restraint is itself potentially dangerous, both to the student and to staff.
Danger to staff is a little more of a gray area, I think, but again restraint should be a last resort.
If there is any possibility that a teacher might need to use physical restraint, then he/she should be specifically trained and certified
in appropriate and acceptable techniques. (These are designed to minimize harm to both student and staff, as inappropriate restraint can lead to injury or even death of the student.)
I can't cover every possible situation that can arise, but a teacher who goes off-BIP had better have reasonable justification for doing so -- and this means that there was danger to a human being. Going off-BIP just because the teacher disagrees with the BIP's effectiveness is never
an acceptable reason, as the BIP is a legal document which must be followed.
ETA: If the BIP of a child who is prone to violence does not address this issue, then the case manager needs to call for an IEP meeting immediately and revise the BIP.