If people would follow the "you shouldn't give anyone permissions to chest if you don't want them to use everything in there to their own personal benefit", the FC chest would be completely useless for anyone but the FC master in the first place. It's obvious the chest is meant to be more than just personal storage space for the FC master, so it makes no sense to defend this argument.

GMs should intervene if a FC members steals stuff from the chest, if it can be proven that the member is aware of the FC rules regarding the use of the chest (a screenshot of chat log when the rules have been explained should work, for example).