Why should we trust a green trusted member? because another green trusted member has left him/her a positive feedback. how could we trust the two green trusted members? because they all are trusted by theymos? but theymos doesn't trust some of the green trusted members.
If I want to trust them then I am allowed to do so. If I believe there is value in the green trust and I wish to make an agreement with one of the I am allowed to do so. I get to decide how much value the trust colour has for ME. Just as you and everyone else here are free to do the same or the opposite its your choice big boy!