Why the word Millennials makes Cringe

Here we have a man who explains his own experience about a young Millennial girl who talked to in an aero plane. She was working in a company which it seemed she wasn't quite motivated about what she had to do. 

Millennials are coming with strength to fight for what they want, but to reach the success first they have to do different things. But he thinks that talking about the behavior of young people without talking about the challenges they face is dumb.