If you find yourself on the opposite side of opinion with the entire management of a company you've found that you don't fit with the company. In this case it doesn't matter if one manager or all managers are objectively bad or not your communication on the way out should be why you feel you didn't have a good fit with the company not why the company should fire manager #14 specifically and expecting them immediately to do it on the word of the 1 guy leaving the company.