This is not a period drama, I don't see any intention at all to do an authentic show about that time period with realistic speech and behavior of the people.

This show is clearly and intentionally just using historic period to highlight universal and timeless problems of immigrants and various aspects of political world related to it. There are obvious elements of current life in events and in the characterizations of the characters here, so from my perspective it doesn't matter how they talk or behave. You place same plot in our days with cars, guns , police and criminals and you won't see any difference.

This is intentional technique, and they did it very well. For a show about martial artist the dialogue is surprisingly well written. That opening scene in episode 8 when they sit and eat, casually talking and joking while there is a pile of dead bodies around them, that was brilliantly written scene.

Hope there will be season 3, any fan should go and sign the open petition to save this show.