Uh... I don't mean to be blunt, but the answer is an obvious yes...
Being told to be someone you aren't will end up with you failing to meet expectations, which in turn will lead to constant guilt and feelings of worthlessness.
Constant feelings of guilt and not feeling worthwhile can cause depression which can then escalate to self abuse, suicidal thoughts and mental illness that can be extremely hard to recover from. One day, they will most certainly have a mental blow out.
While trying to correct certain tendencies is fine, suppressing an entire persona will, most usually, only have negative effects on the person.
Garrett