James McAvoy is being very clever here; one of the things he's especially clever about is accents. I won't belabor the point of why it wouldn't make sense to act out an entire movie in a foreign language -- the point of translation is making foreign books/movies accessible to audiences in other language environments. Unfortunately, in the US translation there's often a tendency to make a movie or text seem foreign by using actor accents or broken grammar respectively.
This convention seems to create an additional barrier between the audience and the work, by constantly reminding the audience that the work if foreign, by intentionally othering and alienating the characters. I find it supremely annoying, for example, when Russian characters in stories by American authors occasionally use Russian words a la Clockwork Orange -- because they are speaking Russian the entire time, they sound NORMAL to each other, and an occasional foreign word serves no other purpose than to exoticize. (I, of course, am not talking about words that have no obvious English equivalents, but perfectly normal ones -- babushka being a very weird favorite for some reason).
I don't get it. A couple of years back I was on a panel that compared several translations of Zamyatin's We, and both the audience and the panel participants seemed to prefer the translations that sounded the most broken, the most alien. I alone liked the one which translated Zamyatin's text into normal English (with a few quirks of the original preserved), and I still remember the vertiginous sense of trying to explain how alienating that broken English felt while realizing that my own accent, in turn, is rendering my point useless (after the panel, several people saw it fit to compliment me on my accent; just FYI.)
So all of this is probably tangentially related to the issue of world SF, or rather lack of translated SF in the US. Sure, some of it is cost and opportunity; but much of it, I suspect, lies in that culture of othering, while failing to admit that much of the SF audience is not looking for a truly alien experience. We like our aliens to be just like us, or at least shown through the eyes of people just like us. Foreign books, written for a foreign audience, assume different frames of reference, and a reader has to do a bit of work decoding them, and, most of all, relating not to him/herself, but a person with different life experience. It is much easier to create a faux difference by inserting an occasional foreign word/broken sentence than to cope with a real difference. This is the main explanation I can come up with for the dearth of translated books but an abundance of books by Americans (and for Americans) writing about other cultures. There's interest in the other, but only presented through a certain lens, and dotted with frequent markers of the otherness -- rather than a genuine desire of much of the audience to understand people coming from other backgrounds. And by defining them in our terms rather than allowing for self-definition and self-representation, the culture of Western-centric entertainment McAvoy is talking about continues. But hey, they are making Tolstoy in translation and with no silly accents. That's good, right?