A phrase from Gray's "Elegy written in Country Churchyard" came to mind as I read your description of the character in James' novel who spoke the phrase in question, ,,, "Some Cromwell guiltless of his country's blood".
I haven't read the novel and don't know the author, so I don't really understand the context.
As for the salvation of mankind, it still doesn't seem possible. Our terrestrial home is itself doomed to a finite life that will limit us - even if nothing else does the job first. I think the unloving competitive instincts of mankind are more likely to find an escape for the species from this fate than the loving ones. Even there the prospect is uncertain.
On a personal or individual basis, however, I believe the comment makes practical sense, I have found that for most of us happiness & peace are choices, not objectives to be sought. People will, to a great degree, reflect back what we show them ourselves in our daily encounters. Thus sympathy begets sympathy, anger begets anger, and joy begets joy. It doesn't always work that way, but enough to be a useful,guide (at least when I am wise enough to remember).