I think too much can be made of the power of words, once we get beyond the obviously true business about overtly offensive language.

For example, "black" and "dark" and so forth have pretty univeral connotations to do with light and shade and not being able to see in the dark and so forth, and scary things happening at night, which are far older than any contacts between people with noticeably different skin colour. That's where an expression like "black-hearted" has its source.

Changing language as a way of signaling a rejection of racist attitudes can be useful. (And it isn't just race where this kind of thing applies - for example it is as relevant in relation to disabilities, particularly learning disabilities)

But that kind of change is just a symbol. If the attitudes don't get changed the new language will be be used with the old attitudes, and will take on the same qualities. And there is a very real danger in going overboard and trying to change language that isn't intended as offensive,and isn't generally understood as offensive either. The effect can be, paradoxically enough, to triviliase issues that are far from trivial.