I've too come across some sketchy stuff (then slowly backed away), but sometimes people need to vent or feel a little deviant. As long as their happy and it isn't hurting anyone I don't see a problem with it... although sometimes I wonder if those communities are a safe haven for people who stray from our norm, or a, I don't want to say breeding ground, but somewhere that encourages people enough that they might loose the distinction between reality and fiction.
I've written some more deviant stuff for Mass Effect on request, and it was an academic exercise, a writing challenge to see if I could. Sometimes it worked, and sometimes it really didn't 
It only gets to be a problem when people 1) don't label properly or 2) insist on a particular headcanon being correct or preferable. But that's really no different IMO from fanfiction that's violent, or gory, or whatever.
Solas: But your people are ignorant children who would of been better off worshipping buttons and frilly cakes for that's about as close as they got to the actual truth.
Solas, hun, just because YOU can't hold your sh*t together over buttons and cakes doesn't mean the rest of us can't handle it 
People tend to take what they find data mining as evidence to insist things should have been this way or that because they are disappointed when it isn't. It's a dangerous thing.
It was the same way with the leaked script for ME3, to the point where Drew Karpyshyn actually commented on it. You only think the datamined/cut stuff is better than what's in-game because it suffers none of the usual cuts and restrictions from having been implemented in the first place. It's no more "real" or canonical than headcanon.
It'd be like people coming across early drafts of Lord of the Rings, and demanding that Frodo be renamed Bingo (yes this is a real thing).