I wear flip flops alot. They are swarvoski crystal flip flops that cost me over $100 and go very nicely with dress pants in the warmer weather. Sorry, I would have never dreamed that I was offending anyone and take a lot of pride in my appearance. I get tons of compliments from people and inquires as to where they can purchase my shoes. Not everyone feels the same way and to each their own I suppose.
I'm not the poster, but I'm thinking that the poster probably was talking about those rubber type flip flops that they sell at Old Navy. There's a time and place for those, and I'll agree that a nice restaurant is not the place for it.
I do think people dress more and more casual nowadays. For me, it's fun getting dressed up every now and then and go to a nice restaurant. Although generally, what people wear don't bother me, but for myself, I enjoy getting all jazzed up and going somewhere nicer.