Obviously he wasn't correct otherwise MLK would've been unsuccessful.
At any rate, MLK didn't exist in a vacuum. It is quite possible that the movement, if it only consisted of people that aligned with MLK, wouldn't have been as successful?
As was Ghandi.
MLK being assassinated doesn't doesn't change the fact that his focus on non-violence was more successful than the contrary position taken by the Black Panthers.
I tend to believe that things happen because they must. It was undeniable that the CRA was going to happen but without strong support from all over the nation due to the tempered approach espoused by MLK, who knows when it would've been realized.