You need a very complex weighing and revocation mechanism because once one bad player is in your web of trust they can become a node along which both other bad players and good players alike can join.
Then I can see who added that bad player and cut off everyone who trusted them (or decrease the trust level if the system allows that).
Build a tree, cut the tree at the first link, now you get rid of all of them. Will have some collateral damage though, but maybe safe to assume actually "good players" can rejoin at another maybe more stable leaf