The only thing I can tell you with the information you gave me is that Illinois like most states is an employment at will
state - meaning you can be disciplined or terminated for any reason that is not otherwise a violation of law. These exceptions are the civil rights protections (e.g., age, race, sex, religion), violations of public policy
(e.g., fired for attending jury duty
, for refusing to break the law, for reporting illegal activity by the employer (aka a "whistleblower
violation"), or having some contractual right to a just cause employment (meaning the employer cannot terminate you without industrial due process - which basically insures a fair and accurate investigation and decision). Without any of these exceptions, courts find that the employer has a legitimate business right to operate its business however it sees fit and the court will not second-guess the employer. These policies and decisions may in fact be awful and clearly not fair or even make good business sense. However, they are not ultimately unlawful.
If the supervisor has a vendetta against you for your attitude, that is not an exception to the "at will" doctrine. We would need some evidence - such as your being discriminated against for your age, race or gender.