The vast majority of humanity values themselves by their correlation to others; they value themselves based on social acceptance; of finding the perfect balance between their identity as individuals and their identity as part of a collective, a group. Consequently, their social capital becomes their primary heuristic for their value and obtaining it becomes a premier social drive.

Putting others down increases your social capital relative to your surroundings, that's why they do it. Making yourself seem something greater than you are is another one, that's why they enact the lies and self-aggrandizement.

Self-described misanthropes on the other hand, determine their value based on the things that they do, based on actions and their results; thus devaluing social capital and valuing genuine things. So when you take such an individual and place them into a crowd of other people who have only social capital, they devalue those around them as they have nothing worth having while the others devalue that individual because they simply cannot understand what it is like to not value social capital at all. It seems like a completely alien mind to them.

Our identities are determined by the things we enjoy and the things that we hate; all our actions consequently revolve around doing things that we like an avoiding that which we hate. So when we "misanthropes" enjoy something genuinely while devaluing social capital and consequently hating people who value social capital over everything (and thus, them appearing to be wasting their lives on it), we are ostracized simply because our identities differ far too greatly from others to be accepted within their spheres of acceptable identities.