No offense, but the statement 'urban chicken keeping is that they attract rats' itself in not true.
Rats, like raccoons, mice, and other creatures, are drawn to food, water, or shelter. One need not keep chickens to attract rats. In fact, I know many dog owners who are careless with storage of dog food who attract rats. However, no one says keeping dogs attracts rats. What of the many people who are careless in storage of their own food and in turn attract rats?
Careless food storage attracting unwanted guests = TRUE.
Urban chickens attracting rats = FALSE.