In the administration of the University System, no applicant shall be denied employment by the Merit Board or by any employer subject to this Act because of race, color, sex, national origin, religious or political affiliations, ancestry, age, marital status, order of protection status, disability, military status, sexual orientation, pregnancy, or unfavorable military discharge, as defined in the Illinois Human Rights Act, except that any applicant for employment may be required as a condition of employment, to sign a valid oath attesting his loyalty to the state and the United States.