If this person had a desk job, I'd agree with you but if someone has a history of mental illness they shouldn't be allowed to get anywhere near the cockpit of a passenger plane. End of story.
We'll need to wait for the proper investigation of course, but if it is confirmed that he indeed had a mental condition that was known to Lufthansa, then it is diffucult to fathom why he has permitted to continue to fly given the strict nature of pilot selection.