Chad should ask his partner if there is any emotional history there; does it trigger a memory? Then they can work on finding less difficult ways to bring up problems when they know why he reacts so strongly.
That’s just how men are. They don’t like to be criticized.
I suggest he take a look at when he’s criticizing his partner: Is it during otherwise stressful times? Bring up issues during a calm, easy time.
He might have to pick and choose which problems he brings up in his relationship if the reaction isn’t worth it.