How does king defend his philosophy of nonviolence against the claim that it is cowardly or passive?

King believes that non-violence is not weak because although physically they do not react but spiritually they are firm in their beliefs and are determine to effect change.  It takes a lot of courage to march amidst a hostile crowd and be beaten and hosed down.  A coward would not last long under those conditions but they did.

if interdependence implies a two-way dependence, and if each partner is equally dependent on the other for success, then there is an equal commitment to the making the partnership successful. the advantage is sustainability of the relationship, the disadvantage is that decisions are "democratic" and therefore may take longer to reach and more likely to be a compromise (which is not always the best solution). as the interdependence moves away from equality, the decisions become more influenced by the more independent partner. in the extreme the relationship becomes more dictatorial and more like "master-slave". generally the relationship has less commitment in both directions and is more likely to be temporary.

if one generalizes (and one shouldn't), equity partnerships, which is probably what is implied by interdependence, can be slow to progress or change but durable. the extreme alternative, independent-dependent partnerships tend to be efficient but more fragile.

hope this but you will have to site your own evidence. : )