Matt's Inside Line (TV Line) - Spoilers
You can find it here: Matt's Inside Line
This is the question/answer that specifically deals with Supernatural.
"I was surprised that Supernatural’s Dean caved so easily to working with the British Men of Letters. Is he now all in like the other Winchesters or will Dean continue to push back against the Brits’ way of hunting? —Lisa
We’ve helpfully updated your question: Considering what the Brits are up to now, with the spying and killing, is Dean going to be feeling pretty vindicated about his initial hesitations? “‘Vindicated’ might be the wrong word,” executive producer Andrew Dabb says, explaining that “there’s some of that, but I don’t think there’s so much that it will be off-putting. Dean went into [the partnership with the British Men of Letters] with his eyes open, and Sam and Mary probably bought the hype a little bit more. Dean’s more of a skeptic. Sam has always been a little bit more a believer, and Mary’s the same way. They both want to make a better world, a monster-free world. The Brits are making progress doing that. So what it comes down to, finally, is the price you’re willing to pay — and once the rubber hits the road, that price is probably too high for our guys.”
So Sam and Mary have only bought into the BMoL hype "a little bit more"? I think they've bought into it a lot more. Sam has always been "a little bit more" of a believer than Dean? I think he's a lot more of a believer than Dean (Houses of the Holy. Dean could be saved from his deal. Ruby. Jumping in the cage with Lucifer would work. Getting the Mark off Dean was possible. Getting Lucifer out of the cage was God telling him to do it. The BMoL. - Sometimes he's right, like with there being a God or Swan Song, but a lot of the time, it's where he also gets lead astray - kind of one of his main traits - wouldn't call it "a little bit more"). Does that mean that if Dabb thinks that Dean's feeling "some" vindication for being right about the BMoL, it will actually be a lot more? ;)
Honestly, the show has already vindicated Dean to the viewers, because we've seen every time the BMoL do something wrong. It's just that his family hasn't had to acknowledge he was right yet. I'm waiting to see when this happens, but until it does, I'm getting more and more annoyed with how right we know Dean is without any of the Winchesters catching onto why, because it makes them all look bad.