If the "no one considers that he is a good sales guy" crowd includes some people who really would know, then your startup is not viable with him in place. You

If the "no one considers that he is a good sales guy" crowd includes some people who really would know, then your startup is not viable with him in place. You'll probably need to leave. But quietly talk to the people who provided you with funding. Even if they have no good ideas for fixing things, you always want to keep your financial backers feeling appreciated, informed, and happy with your conduct.