I think childhood has plenty of “toughening” experiences. Normal sibling rivalry, competitive team and individual sports, chair auditions, challenging coursework, and regular, everyday social interactions will toughen a kid up without leaving them with emotional or physical scars.
I suspect there’s a minority of people who think any unpleasant social interation is tantamount to bullying, and that “getting along” means that everyone in the class is friends with everyone else. But I see nothing wrong with applying the same standards of decorum that we expect in the workplace in schools. I don’t go to work expecting to be insulted or harrassed. Kids shouldn’t either.