I really don't see how the companies placing the ads, aren't going to get hammered for it. But Facebook is doing nothing illegal, unless the ads, were placed for jobs with facebook. Just as newspaper/radio/tv aren't required not to post job adverts that violate the EEOC's rules.
It is also illegal for an employer to recruit new employees in a way that discriminates against them because of their race, color, religion, sex (including gender identity, sexual orientation, and pregnancy), national origin, age (40 or older), disability or genetic information.
For example, an employer's reliance on word-of-mouth recruitment by its mostly Hispanic work force may violate the law if the result is that almost all new hires are Hispanic.
For clarity, According to the EEOC (https://www1.eeoc.gov/laws/practices/index.cfm?renderforprin...)
Recruitment
It is also illegal for an employer to recruit new employees in a way that discriminates against them because of their race, color, religion, sex (including gender identity, sexual orientation, and pregnancy), national origin, age (40 or older), disability or genetic information.
For example, an employer's reliance on word-of-mouth recruitment by its mostly Hispanic work force may violate the law if the result is that almost all new hires are Hispanic.