Right, I don't think it was done out of malice. I think the author wanted to write a cowboy romance and picked this time period because it added drama and angst.
The problem is that slavery and colonization aren't settings where you can just ignore the history in favor of smut. it's going to come across as tonedeaf af.
Yup not out of malice but ignorance. If the author hadn't depicted the characters this way and maybe started off in a different way (instead of having a white savior and master slave dynamic) having chosen this specific timeline, maybe the author cud have highlighted the struggles of the people and showed the absolute pain and desperation of the enslavement of Black people and the colonization of Indigenous population (which is TOO MUCH TO ASK) with and inch of innocent but troubled romance, then maybe we wud have had the hope of finding an absolute masterpiece but nope.

The author shud have done a bit more of their homework before posting the first chapter so confidently... the issue lies with the sensitive timeline that somehow the author decided to handle very carelessly, ending up in ignoring events that truly happened during this era— still wont change the fact that they are one of my favorite yaoi authors!