Sort of what everyone said, which I know is sort of contradictory, but...
I definitely agree that the sponsor's role is to guide one through the steps. Period. If the sponsor has some additional wisdom/experience/knowledge and can offer that up with humility and concern, I think they should do that (at the right time) and then leave it.
As far as a second opinion goes, I would recommend seeing a psychiatrist who specializes in substance abuse. When I first went to my GP seeking help, she prescribed Klonopin and I knew from my research that was a very bad idea. In medical treatment facilities I've heard counselors describe benzos as freeze-dried alcohol. Not one psychiatrist I've seen has ever prescribed a benzo - there are better medications for what ails us. I am not a medical professional and I sure am not telling you what to do. Just offering my experience.
Regardless, if your sponsor doesn't back off this, I think you need to separate and find someone who will put their emphasis on working the steps.
O