Let’s say you have been accused of something at work, whether fairly or unfairly. The employer is investigation the allegations and they are about to interview you, i.e. ask you questions about the allegations to find out your side of the story. This is probably a stressful time and process for you.
One thing you should avoid doing during that investigation is criticizing your employer. Telling the investigator about how awful your boss is, how you are being framed, how the whole process unfair, etc… and showing frustration in any other similar way is not going to help you make the right impression on the investigator. And, it’s certainly not going to improve your chances of completing the investigation in your favor. You simple cannot expect your employer to respond favorably to you in response to harsh criticism, however justified it might be.