California employers can legally discriminate against their employees for any reason except those covered under federal and state anti-discrimination laws. People could be fired for being too attractive without their employer facing legal liability. The same goes for a variety of other discriminatory reasons, including weight and political affiliation.
The at-will termination employment laws of most states allow an employer to fire someone for no reason at all, as long as it is not based on age, disability, national origin, religion, sex, race, genetic information or pregnancy. Sexual orientation and gender identity are believed by some to be sex discrimination, but some courts have ruled that it is not. While the Equal Employment Opportunity Commission has taken the position that it is, federal courts are not bound by its rulings.
Most states allow companies to terminate an employee for engaging in political activities. A person could be fired for expressing their political opinions on-line because freedom of speech does not protect an employee from a private company's actions. Employers are free to fire someone over social media posts that they deem unacceptable. People may be fired for what they do away from work, such as dating a co-worker, smoking cigarettes or marijuana, or having another job.
People who believe that they have been wrongfully discharged may want to meet with an attorney to see what recourse may be available. Legal counsel can examine the circumstances to see if the worker was terminated on the basis of being a member of a protected class. If that is the case, the first step could be to file a claim with the EEOC.