If I start getting negative in an interview, I'm just giving you some free advice before I leave for my next interview....

People interview me for what I have done and can do. If I think what you want me do sucks, I don't want you, whether you would have employed me if I'd have kept my gob shut is utterly irrelevant.

Don't forget I'm interviewing you while you are interviewing me, and the crap joke about the weather and the expectant smile waiting for a sychophantic laugh tells me you're nervous and ill prepared...