There is no definitive answer as it depends on the mood however i can propose several solutions to remedy this. I am listing my solutions from the most useful to least useful.
1)Talk to other players in private and learn their feelings before talking to the pair and telling them that everyone is a bit disturbed by how long they take.
2)Tell them that after five minutes for each minute they talk 10 minutes passes in game. This is a slightly extreme measure but it works really well when you need to hurry things along.
3)Ask the other players in front of those argue whether they are disturbed or not. Chances are they will agree with you. When they say they are disturbed then it will create a certain amount of pressure on the pair to not push it too hard and you won't seem like a jerk for telling them to hurry things along.