I'm glad you said it first, and I couldn't agree more. Not only is it disrespectful to your host (and paying does not give you the privilege of being disrespectful), you are also being disrespectful of the other diners and the enjoyment of their dining experience. I personally have never been uncomfortable in linen slacks and a light collared shirt, especially in the evening air, and women in sundresses look pretty comfortable to me. There's dress casual which is okay, and then there's "don't give a damn" casual, which isn't. Just my old stick in the mud opinion.