If you do not have an employment contract--and most people do not--you are an employee at will. An employee at will may be fired at any time, for any reason--including for doing things that other employees do. As a general matter, the law does not require that employers be fair, logical, or consistent.The exception is that the employer may not single you out for  termination if it is doing so due to a discriminatory reason. Under federal law, it is illegal to discriminate in employment on the basis of race, religion, sex, age over 40, or disability. Washington State adds some additional protected categories: Creed, Color, National Origin,  Marital Status, Family with Children Status, the Use of a Trained Dog Guide or Service Animal by a Person with a Disability, honorably discharged veteran or military status or Sexual Orientation/Gender Identity.If you've been singled out for one of the above reasons, that would seem to be illegal and you may have an employment discrimination claim; otherwise, in the absence of an employment contract, it would be legal.