minecraft isnt hard, if he destroys your base its not that hard to rebuild. and honestly, its ONE guy, how hard can it be for an ENTIRE FACTION to kill ONE guy and take his stuff? not hard. if he is really able to continuously destroy your faction 1) he is cheating, in which case he is banned or 2) you suck at this game and shouldnt be playing anyways.
i mean in the last server i just built a really cool looking church with mossy cobble and stuff and put chests with FREE stuff in them. it was not on owned ground and it stayed standing the entire time until the last bit where everything just started getting destroyed before the map change.
tl;dr seventh appears to be better at minecraft then you