What is the difference between current and former employee?
A current employee is still employed by that particular employer; a former employee is not.
What is the difference between the fight and flight approaches to unfair treatment in the workplace?
No. However, if there is some allegation of abuse or harassment, the other employee can seek a restraining order against you. However, the employer can make your employment contingent on complying with this instruction. If, for example, the company believes that this former employee is seeking secret information or attempting to lure away current employees, they may well be justified in making this a condition of employment.