I often run Steal Away Jordan, a game in which players play slaves in the Antebellum South. In that game, roleplaying the culture is pretty essential.
To encourage it, I often ask leading questions. For example:
Player: "So I go and talk to the overseer."
Me: "Right. When will you do that? Do you just break off from your work and walk towards him?"
Player: "Yeah, I think I would."
Me: "OK. So all the other slaves watch you as you walk towards him. Are you making eye contact with him?"
Player: "No, staring at the ground."
I try not to directly block an idea. For example, I don't say: "You can't just walk up and talk to the overseer!". Instead, I ask the questions.
Oh, and I tell them the consequences, too. Sure, they can talk back to the landowner, but he likes using his whip. Are they OK with that? Then go ahead.
So perhaps there is something similar you can do in your game. For example, if a dwarf wants to talk back to his father, you could say: "What, you're going to say that to his face? You know that could destroy the family honour?". And, if they're OK with that, then great. But you've asked the questions and pointed out the consequence.
Hope that's useful. (Steal Away Jordan can be a controversial game, but it's a good one, and useful for this thread, I think.)