I am expecting exactly this. Talk to your faction, not just one member and solve it. "I cannot control my members while I am not there" isn't an excuse for player behaviour. I am not asking you to act as parents of your members, just sit down, speak with them or set some kind of internal rules which would prevent situation like this one to happen.
I led several factions, one of them in Liberty and I could see development of 5th fleet. You can control your members.
