My approach is typically not to be a screamer or a yeller, though I can be. But if I had yelled all the time, even at my own children, they'd never listen to me. When I do get upset, there's a message there. I don't believe players make mistakes on purpose. It's our job as coaches to teach players and help them not make mistakes.
Coaches have to develop trust in players.
If a cornerback who runs a 4.8 in the 40 can't cover a 4.4 receiver, it makes common sense not to ask him to do it. Fisher's approach has worked. He's not an ogre on the field. He allows you to work. He's adaptable, and he does a really good job of having a pulse from the team.