I'll just go over my beefs in chronological order.
So, David starts torturing Oliver (thinking the Shadow King is still inside him) for the info he needs to find Syd. So far so good. But Oliver refuses to give up the info. David tortures him to near death, and then suddenly Oliver gives it up?! I mean, why then? Why not right away?
Then right as David is about to fulfill his destiny and bash Farouk's head in, Syd pulls a 180 from two episodes ago solely because Farouk (in Melanie's body) was in her ear. There better have been some unshown brainwashing going on (which would be weak writing also), because if not, that was completely out of character. So, she decides to kill her true love, and then Lenny's bullet collides with it in mid-air?! With no powers being around to explain why that happened?! They had better give a supernatural or time-paradox reason for that later.
And while all of that was stupid, I'm sure what bugged you the most was the 180 that EVERYONE decides to pull when they trap David and accuse him of crimes he hasn't commited yet. Not only future crimes, but crimes committed in a future that NO LONGER EXISTS because David DID NOT bash Farouk's head in. Ok sure, Farouk got loose and pulled a mind fuk on Syd ...and Cary? ...and the moustach ladies?! Farouk, the guy they had to destroy at all costs, is now suddenly in good enough graces to be a witness against the best weapon they have?! They kind of hint that maybe we have been having the story told to us by an unreliable narrator all along when they have Syd and David's quick aside with the "What about God loves sinners best?!" and her "You drugged me and had sex with me" retort. Um, I don't actually remember that detail from season one, but David seems to begrudingly accept that it may be technically, factually true. Maybe the bulk of season 1 and 2's events are just presented to us through the eyes of a narcisistic schizophrenic and David really was the villain all along, but that seems uber hacky as well. But even if Syd and David got together on a drug-induced date rape, that seems to fit in really well with the "God loves sinners" line Syd gave David just TWO EPISODES AGO. The whole quick part with Cary watching the reply of the aftermath of the desert showdown where David erases Syd's memory of trying to kill him and mumbles "Treachery!" was so horsefeathering dumb. I guess he conveniently missed the 3 minutes of dialouge just before that where Syd TRIED TO KILL HIM FOR NO GOOD REASON.
So yeah, with only David acting rationally, he peaces out and goes to free his sister possessed by a disembodied junkie to have lots of sex with her in a bone-littered tent. You do you David!