Hilchos Lashon Hara chapter 10, section 12
This applies even more if the person did not harm a person but only failed to provide some benefit he should have, such as a loan, charity, or hospitality. If one reveals this in order to disparage him it is absolute lashon hara as we wrote above (5:1). One also transgresses other negative commands as explained there. Many people stumble in this matter. If they are not well received in a town, they disparage the important people there for not helping them. This is even worse if he disparages the whole town and a terrible sin. For lashon hara applies when speaking about an individual and even when speaking of a whole Torah observant town.