This is a likely cause of it.
Shadow said it best just lay it out there that you don't want his advice, but do it politely so he doesn't get all hurt over it.
If that doesn't work throw a dumbell at his head, glare at him, then start howling like an angry monkey. He'll probably get the point then.
This is where being a big tattooed powerlifter is nice, I just glare at people bugging me and they go away.
Cheers,
Scotsman