If they accused Jesus of having a devil you can expect the same treatment. Ignorance of the Father amounts to ignorance of the Son. Father and Son are both true God. Jesus is not excusing these people but revealingtheir guilt. The worst ignorance is ignorance of the Father and His Son.
Natural man is spiritually blind.
If any man is in Christ he is a new creature. Old things have passed away. All is new. Think of the Apostle Paul before and after conversion. If you would know Me, you would know also My Father.