Historically, it seemed to me that many teachers (at all levels) took pains to prepare students to handle disagreement in a healthy way. More recently, it seem

Historically, it seemed to me that many teachers (at all levels) took pains to prepare students to handle disagreement in a healthy way. More recently, it seems that our culture has changed, and that students are being not just indulged, but even encouraged to respond in the unfortunate manner that you describe.