I am not a lawyer, but I am directly quoting the US Government Agency that is responsible for enforcing these laws.
US employment law prohibits a large number of normally OK employment practices when they have a disparate impact on protected classes.
> 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. [0]
I'm not. But I don't believe you are right - advertising in a magazine doesn't exclude people just because their demographic doesn't target them.
If you ran a job ad for a make-up person in women's magazine there is nothing stopping a man who is also interested in make up seeing it and applying.
That is different to the Facebook system, where there was no way for someone from the excluded classes to see the ad.