This was the plan with which they all came up, they knew that they could not barge inside the manor and just declare that the Chen sisters were not humans but demonic beings. If they did that then they will be treated as someone who had lost their minds which was why they decided to dump the pot of blame on the unconscious Commander Chen, though this step was a bit ruthless, there was no other choice.
Old Master Yan had heard from his sons that the demonic forms of the two Chen sisters were scary and terrifying. They even had the power to lull a man to do their bidding unless the will of that man was strong enough to ignore that voice, no sane man would take on something as dangerous as that and even face it with a smile on their face which was why Old master Yan decided that he was going to use the unconscious Commander Chen as a shield.
