
Hello there! Assuming that there are no OOC issues going on here (people taking other character's attitudes personally OOC, people using a character's mean attitude to vent OOC nastiness, etc.) and that this is the actual problem (there are a lot of issues that can happening in an FC, a dark/evil themed one especially), I'd say that since this a problem that stems from IC interactions, the key to fixing it is largely IC.
Assuming your FC also functions as some sort of group or organization IC, whoever is in charge probably wants to amass more members and doesn't want people bailing all the time. Whoever the IC leadership is needs to tell their FC mates to play nice and be welcoming with the fresh blood so they don't scare them off. IC rewards could be given to those who follow the rules, and punishment dealt to those who don't. On top of making some leeway in solving the problem of turnover, it could also give you some RP opportunities.
Assuming your FC also functions as some sort of group or organization IC, whoever is in charge probably wants to amass more members and doesn't want people bailing all the time. Whoever the IC leadership is needs to tell their FC mates to play nice and be welcoming with the fresh blood so they don't scare them off. IC rewards could be given to those who follow the rules, and punishment dealt to those who don't. On top of making some leeway in solving the problem of turnover, it could also give you some RP opportunities.