First of all if you are a business owner with less than 15 employees, the discrimination law (Title VII) is not applicable to your choice of hiring.
So the example of being discriminative about the person who rents your house is not a valid example.
Secondly, all these laws are good and beautiful. But do they make you hire a person you really don't like based on gender or whatever else the reason that might be? You simply would tell them they are not qualified compared to other applicants. So what's the use of having laws that are useless? They keep the face of your country. The US is supposed to be the place of equal opportunity for all people regardless of race, sex, blah blah blah.
My personal experience is an ugly one. It took me a little while to know what's exactly going on, but I found out that I was hired with a salary less than the amount that's supposed to be paid to a person of my qualifications, although laws require the employer to pay the equal amount to an alien worker as what he/she pays to a US citizen. The law is there to protect the rights of the US citizens so that alien workers would not get the jobs because they'd get paid less. There was not much to be done really. Should I have hired an attorney to pay whatever I've earned to eliminate the source of my income? Get real people.
Title VII and the ADA cover all private employers, state and local governments, and education institutions
that employ 15 or more individuals. These laws also cover private and public employment agencies, labor organizations, and joint labor management committees controlling apprenticeship and training.
Source (Title VII of the Civil Rights Act of 1964 (Title VII), which prohibits employment discrimination based on race, color, religion, sex, or national origin.)
Title VII Also it is further explained here:
TITLE VII, CIVIL RIGHTS ACT OF 1964 (AS AMENDED BY EEO ACT, 1972)
Prohibits discrimination on the basis of color, race, religion, sex, or national origin. Covers all employers with 15 or more persons, all educational institutions, public or private, state and local governments, public and private agencies, labor unions with 15 or more members, joint labor-management committees for apprenticeship and training. Prohibits practices identified by statistically determined adverse impact as well as intentional unequal treatment. Decisions concerning hiring, placement, training, promotion, termination and layoff are covered. Title VII established the EEOC (Equal Employment Opportunity Commission) to enforce the law. The amendment in 1972 enables the EEOC to enforce Title VII through court action.
Source 
