I wonder how fine that legal line is when an outreach program is using Facebook advertisement. How common is that they tick that gender box rather than adding some line of "women and people of color strongly encouraged to apply".

Which law is that specifically?

And, as a business owner, please tell me why it would not be in my best interest to hire the best person for the job?

The Civil Rights Act of 1964, Title VII, which was codified as Subchapter VI of Chapter 21 of title 42 of the United States Code, and was later extended by the Pregnancy Discrimination Act of 1978, Age Discrimination in Employment Act, and Americans with Disabilities Act of 1990.

It is in your best interest to hire the best person for the job, but if you determine who is "best" based on inclusion or exclusion from a protected class then you are illegally discriminating (except for in some specific cases such as the sex and race of actors, and where disabilities can not be reasonably accommodated for).

There's no mention of protected class in Title VII. Or the entire Civil Rights Act of 1964 [0]. Try again.

[0] https://www.ourdocuments.gov/doc.php?flash=true&doc=97&page=...

Protected Class: The groups protected from the employment discrimination by law. These groups include men and women on the basis of sex; any group which shares a common race, religion, color, or national origin; people over 40; and people with physical or mental handicaps. Every U.S. citizen is a member of some protected class, and is entitled to the benefits of EEO law. However, the EEO laws were passed to correct a history of unfavorable treatment of women and minority group members. [0]

[0] https://www.archives.gov/eeo/terminology.html

It's the term used to denote the groups protected by a number of different laws, the individual laws describe the classes specifically. This is all well established law and terminology, and anyone who takes part in any hiring process in the US should be versed in all of this.

You're being intentionally obtuse.

Thanks for the information.

Civil rights act, title 7 IIRC

As with most laws, because the government will send some lawyer to hurt you if you don't.