First of all individuals with mental illnesses should be treated with respect and civility. Individuals with mental illnesses can be good friends, brothers, sisters, sons and daughters. That said if all stigma against the mentally ill were to end individuals with major mental illnesses would still have major difficulties. Treatments for mental illnesses frequently do not work and very frequently are only partially effective. Even with appropriate treatment the mentally ill can still be mentally interesting to the point of be disabled. Taking meds as prescribed frequently does not end the disability.
The battle against stigma is terrific if it means that the mentally ill should be treated with respect and civility, that caricatures of the mentally ill must be shunned, and that each individual with a mental illness must be viewed as an individual not as a group representative. If battling stigma means treatment + no stigma = no disability then the battle against stigma is pushing a false narrative.