A real leader protects the team’s name when the team isn’t around to hear it.

What you say about your team when none of them can hear it is the real position you hold. Running them down to outsiders buys you a bit of distance and costs the group something nobody watches happen. Whoever is listening also does the math immediately: if that is how you talk about them, that is how you will talk about me. Loyalty that only operates inside the room is not loyalty.

When somebody invites you to trash a teammate, decline without making a speech about it. Offer the useful version of the truth or say nothing. Take the complaint to the person it belongs to.