unable to differentiate good from bad (idiom); not to know what's good for one; unable to recognize others' good intentions

bad; wicked; evil; Kangxi radical 78

unable to tell good from bad (idiom); undiscriminating

to break the law and commit crimes (idiom); malefactor; evildoer; to perpetrate outrages

to persuade using all possible arguments (idiom); to act good cop and bad cop in turn