Forgive me, but this position is one of absolute impotence.
Your solution is a "mass culling", but you are without the power to put such a plan into action. Furthermore, you know that this type of solution is unlikely to gain any sort of mainstream approval.
Further, why would in-laws need to be culled if your solution relies on genetically based criteria?
Personally, I don't think that greed or selfishness are traits of a psychotic mind. They are human flaws, present in nearly every person on this planet. You can't get rid of these traits - they are inherent survival instincts, found in all of us.