The Charmed Ones, have been possessed by various demons and warlocks many times. Yet, they couldn’t cut Cole some slack that he was possessed by the Source. Yes, Cole should’ve been honest that the Seer tricked him into becoming the next Source but the Source overpowered and controlled his body to the point where Cole couldn’t take control his body and mind even if he wanted to which is why it’s heartbreaking and frustrating the writers ruined Cole’s progress for redemption and happiness. Cole did not enjoy being evil, because he was miserable and the original Source had his father’s soul for at least 100 years as leverage. I wouldn’t be surprised if Cole’s mother, never loved or cared about her son because she forced him to go through the demonic trainings.