|In the first place, his numbers our wrong. There is no way that ten people are willing to take your job if they knew about him.|
He may have the title of manager, but he is not acting like one. A manager who makes mean-spirited comments to his employees generates dissatisfaction and distrust, and typically shows marginal managerial skills in other areas as well. It is possible that senior management is already aware that he is a weak link, and that he is managing like the missing link.
Since your manager has demonstrated his skill in silencing discussions before they get started, several of you should approach the next level of management to discuss your concerns. One of the most effective ways to structure this meeting is to present specific examples of your manager's questionable actions, and then ask the senior manager what he or she suggests you do from this point.
It is possible that this manager will commit to look into the situation and get back to you within a specified period of time. It is also possible that you will be ignored or even chastised. This manager's reaction will tell you a great deal about where the company is going and whether you should be going.