What, his theory that biological traits become either more or less common in a population as a function of the effect of inherited traits on the differential reproductive success of organisms interacting with their environment?

Could you elaborate on how a guy getting scammed proves this right? Maybe you can demonstrate that people with Nigerian ancestry are less likely to fall for this kind of scam (since their ancestors lived in an environment with selective pressure to avoid the scams)?

Do explain how this prove's Darwin's theory...

Or perhaps you meant that Darwinian theory would conclude that this man is likely to purge himself from the genetic pool?