Sadly, that is simply not true. In California, and I'm almost sure in every other state and perhaps in other jurisdictions as well, employment is presumed to be at-will. This means a private employer can terminate the employee whenever they want, regardless of whether they have good reason, and have no obligation whatsoever to provide factual evidence to support the termination, or even to give any reason at all, or to give any notice. The only exceptions to this are if there is a specific contract that states that the employee can only be terminated with good cause (which almost never exists any more) or if the real reason for the termination can be shown to be discriminatory (e.g., based on the membership in some protected class such as race, gender, age, religion, disability or marital status) or otherwise violates some public policy (e.g., in retaliation for whistleblowing or making a safety complaint, or for refusing to do some illegal act).
Quote: But, even a wrongly fired employee can file a damages suit, the owner needs to show just cause and factual evidence that support the termination.
This is only true of private employers. Public employers (governmental entities) are held to a higher standard of due process. But if you are employeed by a private company or individual (including a non-profit) and you think that you have a right not to be fired unfairly, in most cases you would be wrong. At least here in the land of the free and the brave, of truth, justice and the American way. Certainly here in California, and I believe that the other states have similar laws.
As an employment law specialist, this is the largest misconception that I deal with. I would conservatively say that on average I speak to at least one person a day who has his own personal story of how unjustly they were treated, who is sure they have an ironclad suit for wrongful termination, and to whom I have say "yes you were screwed over, but sorry, there isn't a damn thing you can do about it."
Not the funnest part of my job, as you can imagine.