Suppose for a minute that we have a person who's utterly dissatisfied with life. People are cruel, dates are mindgames, beauty is sold to make money for some rich numb asshole's already big pocket, any effort to help the world is without hope or use - and so on. This is a person who goes on with his office job he hates, out of mere survival instinct rather than out of any sort of hope; once he realizes he doesn't have to go to work, he'll abandon it, too, and contemplating suicide won't come longly after.

Suppose that he's utterly convinced that life is shit, because his - oh goodness, was it shit. He's convinced that people are inheritently awful beings, that society drives us all insane while pretending to try and help and make things better, that love is an illusion, a narcissistic facade people put on so that others - those the "lovers" have the most use from - won't run away from them in horror after they learn what those people really are, that we carry on solely because our bodies - animal bodies - tell us that somewhy, we have to survive and procreate, just like fucking bacteria...

You get the idea. How do you convince the guy otherwise? Do you, even? Whether you do, why?