It is a generational thing.
In the days when these were written, indigenous members of population in our colonies (narrowly avoided saying "natives") were usually only seen in those places, and by British people sent there to, in effect, rule over them.
Anyone born post-WW2 will be more familiar with non-white faces, in addition to which most Commonwealth countries are now self-governing, and rightly take their place at the UN and other international fora. Many also came to Britain to be educated, and we came across polished cultured individuals.
Our experience is of comparatively small numbers of immigrants, and we can more readily accept them as equals, whereas in USA's Southern states, there were huge numbers of former slaves vying with the locals for work, and they have taken longer to assimilate these attitudes.
Barnes wasn't asking for revisions to texts, merely pointing out that prevalent attitudes of a bygone era are passed on if one reads them uncritically - but who with any education does? I suspect that those who are likely be influenced by them won't read them anyway.