Code:
Facebook Ad
to some mainstream site
Post promotion (post booster) ->link on post to some mainstream site (cheaper)
↓
No adult links on the landing page
↓
Maybe a few MA PG SFW deep link ads
↓
From those linked pages links to adult content
Maybe experiment with that filter idea. Facebook ad monitors are probably busy (or lazy) they are going to form their judgment on the landing page of the ad usually. You may get 1:50 or 1:100 to make it to the adult content -- the ROMI on the cost of the ads might make this a colossal waste of time.