Why does King go into such detail to explain the basic principles and process of the nonviolent protest movement?

Answer: Non violence doesn't mean inaction

Explanation:

King had to explain the main idea of non violence because many thought that it meant inaction, when actually, it meant the opposite.

One of the main purposes was not to defeat the enemy but to gain its confidence and friendship.

Also, it focuses on the concept of receiving agression without retaliation, that means to ressist actions without answering aggressively to them.

It is also important to consider that, although these acts are against violent groups, the aim is to defeat a higher power (in King's case, racial discrimination)