Negative team member

[T967]

Our team has a problem. We have one or two members that can be very very negative. On top of that one of these people is a mentor. Most of the team is afraid to confront them about it because in the past they have never reacted well to that sort of thing. Both think that everyone in the group try to undermined them, and that we absolutely WON'T be able to accomplish things the building team set out to do. And finally if it isn't their idea, they immediately attack that idea and find every little thing wrong with it or why they think it will NEVER work. Our team is suffering and our parents and team aren't sure what to do. Does anyone have any suggestions or experience with this?