Do you really think that Sadam Hussein, or Adolf Hitler, weren't bad when they were student, they just had bad teachers?? Bhaaaaaa! . Some people born with a psychotic nature that no teacher can rectify! Don't take from people the responsibility of their action!
I think that the original post did not refer to personality, but to learning capability.
I believe that almost everyone and everything alive can be trained, it's just a matter of finding the proper motivation. Whether they learn to use what they've learned is an entirely different topic.
I am a teacher more than 25 years now, and I have my share of students that didn't
Gave a d,,,, about their study's or future! We have here a proverb that say" you can bring the horse to the water but you can't force hime to drink!"