The British novelist L. P. Hartley famously observed, “The past is a foreign country; they do things differently there.”
This is a true thing, and the source of great and recurring headaches for writers of historical fiction, alternate history, historical fantasy, and historical romance (as well as any other fiction, genre or not, that deals with time past rather than time present or time future.) Readers today are, or at least like to think that they are, enlightened and forward-thinking ; and when they read for pleasure, they want the characters they identify with to share their values.
At which point they run headfirst into the unfortunate fact that even historical figures who were howlingly progressive by the standards of their day are likely to exhibit turns of thought and vocabulary which can leave their modern ideological descendants gobsmacked.
I don’t mind it when a historical romance elides or passes over stuff like that; conversely, it irritates me no end when a writer feels obliged to make his/her characters progressive before their time, as it were. Granted, in almost every age you can find people whose attitudes and beliefs were more in line with those of our era than with their own . . . but their contemporaries usually regarded them as whackaloons. And again, granted, sometimes that attitudinal disjunction is the whole point of the story, but if it isn’t, it can be an almighty distraction from whatever the point of the story actually is.
This is, alas, one of those writing problems with no easy solution. Which way you go is your own choice, based — ideally — on the nature of the story you want to tell and the expectations of the audience you want to tell it to and your own ideas about the relationship between truth and fiction. But it’s a sad fact that no matter which path you choose to travel, at least some of your potential readers are going to think that you picked the wrong one, and are not going to be shy about saying so.
Hey — nobody ever said this job was going to be easy.