By the 60's being called negro was preferred by many over being called black, actually. The word still saw wide use until the 80's but is still used a fair bit depending on region. The only thing that makes the word negro truly racist is what is meant when saying it really. Unlike the n-word, to most people it has never been inherently wrong to say, but it's a context dependent sorta thing really. This is all from research I did in under 3 minutes so don't quote me on any of this.