Abuse and consensual play are two different things. In a perfect world the dominance would occur naturally without negotiating boundaries, limits or safety. The fact is this is not a perfect world and certain things have to be discussed. There has to be consent either within the scene or within the context of the total relationship. One person determines what will happen.
Knowledgeable consent is given to the scene by all parties.
No consent is asked for or given. Alcohol and drugs are often used before an episode of abuse. After an episode of abuse the people involved feel bad. The above is paraphrased from a handout I saw at a meeting of The Eulenspiegel Society. People are there to have fun not solve your problems.