- Relative power of a larger business to a job applicant greater than a small business.
- Market forces that would punish discriminatory small businesses operate less efficiently against big ones.
- Discrimination by a small number of large firms quickly becomes a problem for applicants.
- Small firms are usually closely held while large ones have more owners or are publicly held, so the level of regulatory intrusion on an owner is greater for a larger firm.
- Breaking a society-wide discriminatory collusion only requires enforcement against some actors, and market forces will bring along the rest.
- Larger businesses "feel" more public, so public regulation is more appropriate for them.
What this fails to acknowledge is that culture is a powerful force intruding on private agreements and on markets, so it takes a long time for anti-discriminatory laws against large businesses to modify small business discrimination. Some libertarians think discrimination in the American South would have disappeared even without federal laws. I agree that change in the rest of the US would've affected the South, but they'd be years behind where they are now, which is still bad in many places.
This doesn't tell us what the balancing point should be between small business and big business. It depends partially on the level of intrusion. Requiring all businesses with public accommodations to serve everyone is less of an intrusion than requiring them to hire everyone. It all depends on the individual issue. The point though is that applying the law only to larger businesses isn't just a compromise, it actually makes sense.