Don't protect people from meeting the consequences of their actions. Kids included.
In my experience, the reason why people get away with treating others wrong or don't extract lessons from situations, is that they are not facing any consequences.
If somebody is not respecting the boundaries you transparently set, create consequences for them. If you were not transparent with the boundaries, accept the consequences of people breaking them.
If someone abuses you emotionally, make it freaking public. Doesn't matter if it's a promising young men or a promising young woman. Doesn't matter if somebody asks you not to.
Etc, etc, etc...