I don't understand how this has come to pass.

Where did the idea that discomforting material should be avoided arise? Is it ok to speak of painful material if no one that can easily sympathize with the wronged group is present? Can a group of whites, blacks, and latinos, learn and speak about the Rape of Nanking, but only in an educational setting where no students of Japanese or Chinese are present? Or only Chinese students? Can we not speak of the Holocaust if a Jewish student wishes to avoid the topic? What about the great-grandchild of a Nazi?

Can someone of college age explain this phenomenon to me? What is the motivation behind it?

People these days have grown up coddled and protected by their parents. Physically, emotionally, intellectually. It has created everything from ignorance, to laziness, to entitlement. It's crazy to say this, but sometimes I think a lot of these people want to feel victimized because not only does it bring them attention, but it also brings them a sense of comfort when their perceived victimization eventually becomes validated.