I think that Dr. King's ethical frame of reference is rooted in the idea that he would not allow someone else to control how he was to act.  In its most basic definition, violence as a response is ceding control to another force.  When one person uses violence, the tendency to retaliate with violence is where Dr. King argues a surrender of moral ground happens.  For Dr. King, the entire fight against injustice is a moral battle in which one should not acquiesce to a lesser form of moral standing.  It is here where Dr. King's view of nonviolence is one of ethical or moral stature.  This is one realm in which nonviolence is the best way to fight injustice, as it seeks to morally transform all participants.  It does not silence voices as much as accentuating their presence.  For Dr. King, violence for violence sake only demonstrates multiple people losing their presence of moral standing.  If individuals seek to aspire to a higher moral plane, one of transcendence and permanence in a world of contingency, Dr. King believes that individuals have embodied a standard that is ethically incorruptible.  I think that this is where Dr. King's approach can be seen as the best to injustice as it integrates more people and includes more voices as opposed to silencing them.