We have power to act and and to influence another person's journey with mental illness, but we do not have all the power.
A diagnosis is not an assessment of who you are. It is a description of the symptoms you are experiencing. Some diagnosis have more stigma attached than others and some can help to bring life-changing clarity to an individual, directing them towards needed help.
Medication has its limits. It will not provide a healthy environment, social support, the tools to manage difficult situations, or to heal from major crisis or traumatic events and should not be solely relied on for these things.