Promoting members gives them significant responsibilities. If they aren’t prepared for the role or don’t take it seriously, it could adversely affect your Team. Screen your members carefully and promote only those you know and trust.
For example, Vice Captains can kick almost anybody in the Team. This leaves a lot of room for dirty politics if mishandled.
Kicking people for no reason might be a mean thing, but it’s not against the rules. So, preventing it is up to you!
We can’t retroactively change Team dynamics in the event of one bad apple. We like each Team to be pretty much independent.