If what your source says is true, that is a stab in the back from your former co-workers. I bet they are saying that because if you join their work, they know they will look bad. (Little do they realize they do already.) If this manager has any sense, I doubt he will consider that info true from the guys he's planning on firing. Just stay calm and let the dice roll where they may. If that manager believes their lies, then you are better off not working for him.