Anything can be inappropriate if not correctly applied.
Psychological non violent punishment can also be far worse than physical when done to extremes.
If we spank a child, we are supposedly teaching violent behavior, yet if we put a child in a corner are we teaching it is ok to detain people? To force people into situations and override their free will? We can't equate discipline of children to the rules of adult society. If we do, then any discipline will fail the test.
Basically any approach can be done incorrectly and can be abused. Locking a child in a room for a day is non violent, but certainly most agree this is worse than a physical slap on the wrist.
I have personally found that consistency in whatever method you use is more of a substantial variable in the success than the chosen method. Consistency is likely to improve your results better than escalation of whatever punishment you use.
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