Simple; during the work hours employee is at disposal of employer and expected to perform assigned duties.
IT is as simple as that; Employee should acquire skills to handle the bosses and learn to deliver the tasks by performing the tasks.
Then subordinate will escape from pressure and won’t have to say NO.
Saying NO may be found offensive and other tactical pressures may come.
So employee should avid saying blunt; NO.
Saying NO and saying yes both are skills.
Like any skill employee can acquire every skill.
Simple said avoid saying blunt NO.