The human mind is very complex, and there are many ways to divide it up into halves to make sense of it, which are useful as long as you don't take them too literally. One big oversimplification here is:

controls the slave in two ways: direct reinforcement via pain and pleasure, and the ability to perform surgery on the slave's terminal values. ... it has no direct way to control the agent's actions, which is left up to the slave. A better story would have the master also messing with slave beliefs, and other cached combinations of values and beliefs.

To make sense of compromise, we must make sense of a conflict of values. In this story there are delays and imprecision in the master noticing and adjusting slave values etc. The slave also suffers from not being able to anticipate its changes in values. So a compromise would have the slave holding values that do not need to be adjusted as often, because they are more in tune with ultimate master values. This could be done while still preserving the slaves illusion of control, which is important to the slave but not the master. A big problem however is that hypocrisy, the difference between slave and master values, is often useful in convincing other folks to associate with this person. So reducing internal conflict might come at the expense of the substantial costs of more external honestly.