From the research I've conducted, it seems to be that he supported riots saying that it was a necessity, and that abolishing discriminatory laws was not enough. He may have thought that riots were indeed not done in the purpose to achieve societal strength, but rather as an expression of struggle. I may have a few things wrong so I'd very much like the take you guys have on it.
This post by /u/USReligionScholar may be of assistance:
King was condemnatory of violent protests, though he understood that violent action had roots in the oppression of black communities. In his last book, Where Do We Go from Here? Chaos or Community, King calls riots the “the language of the unheard” and “the desperate suicidal cry of one who is so fed up with his cave existence that he asserts he would rather be dead than ignored.” He writes specifically about the Watts riots, saying:
“Occasionally Negros contend that the 1965 Watts riots and other riots in various cities represented effective civil rights action. But those who express this view always end up stumbling with words when asked what concrete gains have been won as a result…. Nowhere have riots won any concreate improvement such as have the organized protest demonstrations.”