It doesn’t have to be…
Are you supporting nazi’s cause you’re buying wolfenstein games?
Are you supporting Russia by liking a Russian song?
Are you supporting human trafficking and sex slavery by watching a movie about it?
The game might not even have blatant racism in it. It might not even have “true to history” racism in it. If the book is old enough it might be that even no rights were owed.
Long story short, if the game is good and doesn’t do anything inherently wrong, don’t care about it.