Again, I have to reiterate that "selling" is not really what i meant to say. I just couldn't think of another way to put it. However, you did answer the question I was trying to ask. That question being how do you get around a client who is asking for sonically ridiculous things when you know, in your heart and brain, that it won't work. On the level that i'm working(the bottom!), the local bands are only too happy to say "produced by x", in order to give their recording a more official look, I guess? Regardless, like you said, it sucks when you're given that credit and yet had no say in what ultimately became the final product. There is no nice way I can think of to say "Hey, don't put my name on this". No matter how you say it, you chance offending the client or, worse yet, losing them to your competition. Now, if the client goes somewhere else because they just don't dig your facility/vibe/equipment/etc. that's fine. I know damn well that my place isn't for everyone. However, if you lose them because you've pissed them off or insulted them, that can get around a very small music scene VERY quickly. Being on Long Island, I can't walk down the street without tripping over a power cord attached to some kid's Digi002 who is selling time out of his house for $15 an hour. Needless to say, I don't want to piss off ANYONE.
So, in closing, the real question was how do you help the client achieve their vision without pissing them off AND without making yourself suffer the consequences for their choices.
By the way, thanks to everyone who responded.