How much freedom should you have to criticize your employer

Unlimited

Explanation:

A firm is made up of its workers. Its productivity is dependant on the employee productivity and outcome. This is why employee satisfaction is considered a big thing and is being researched on extensively now,

As new talent comes in, they have a better idea of the market and are filled with new and innovative ideas. The employees must be allowed complete freedom to criticise their employer wherever they feel necessary but in  a respectful manner to not turn it into a fight.

This would lead the employer to rethink his ideas and decisions to better coincide with the company's goals and ambitions to achieve higher productivity.

On the contrary, if employees are not allowed to do so, the company could fall into redundancy.