managers who do not admit their mistakes and managers who cover up their mistakes

this is a good question:

I am currently working as a supervisor in a supermarket. I had an argument recently with the manager and It was clearly not my fault. Then in the end parang ako pa ang may kasalanan. Pansin ko most of the time she covers her mistakes. Parang babaligtaran niya ang story then ikaw ang magiging kawawa in the end. Tipong magaling talaga maghugas kamay.I am just wondering if its really part of the Manager's role? Ganyan ba ang being professional sa work? Kasi in my place, If I have a mistake when it comes to work, I usually admit it. But now, I felt unfair, kasi most of them they usually cover up their mistakes.