A-Jay Leitch-Smith opened the scoring and Max Clayton and Mathias Pogba both bagged braces as the Railwaymen made it 20 games unbeaten under manager Steve Davis.
The visitors actually created more chances than their hosts but poor finishing and woeful defending against Crewe's fluid, mobile and pacy attack meant the game was over as a contest by half-time.
"That was the worst defensive display I have ever seen. They tortured us," Cooper said. "I am really hurting after that and if the players aren't feeling it too they can leave. I don't want to work with players who don't hurt after that.
"You can't make silly mistakes like we did and expect to get away with them at this level. I was actually really looking forward to the game after the pre-season we have had and after the first 10 minutes I thought we looked sharp.
"But then it was bang, bang, bang and we were 3-0 down and I couldn't believe what I was watching. When the fourth and fifth went in it was just embarrassing. The back four looked like they had never met each other and big men were getting knocked around by little boys."