As I understand it, the sub being flagged NSFW as a whole means Reddit can’t sell ads on it, whereas general subs with NSFW content are considered fine (like AskReddit, where “what’s the sexiest sex you’ve ever sexed?” comes up about twice a week). The subs would need to be flooded with NSFW content that is upvoted above anything SFW for several days and a campaign to highlight this to advertisers to effect change in this way, and I’m sure the admins would yell at them before it got that far and the moderators would crumble again.