My response would be..."So my car made those sounds from the factory? So a brand new corvette with a sport suspension makes those noises? And please tell me how exactly a SC will affect the suspension?"
Yeah, they are blowing smoke up your ass. I wouldn't take it anywhere else. I would go over the guys head. I have heard the saying before: "If you go high enough, there is one guy that can make the decision to get things done." I have gone over people's head before to get stuff taken care of. If I don't get the service I expect, I go higher. Screw the guy that told you that. Go higher and get it taken care of.
