Still looking for that MLK quote, but here’s another good one:

«Negroes are human, not superhuman. Like all people, they have differing personalities, diverse financial interests and varied aspirations. There are Negroes who will never fight for freedom. There are Negroes who seek profit for themselves alone from the struggle. There are even some Negroes who will go over to the other side. These facts should distress no one. Every minority and every people has its share of opportunists, traitors, freeloaders and escapists. The hammer blows of discrimination, poverty and segregation must warp and corrupt some. No one can pretend that because a people may be oppressed, every individual member is virtuous and worthy. The real issue is whether in the great mass the dominant characteristics are decency, honor and courage.»

https://www.amherst.edu/library/archives/holdings/mlk/transcript

(I believe they are.)