Surely it's the national federation that must be held accountable for checking a player's status. To throw the onus completely onto FIFA appears unrealistic even if they ARE the world governing body.
Checking the authenticity of documents in Qatar probably only applies for work permits which, I assume, Emerson would have needed to obtain.
I agree that FIFA should release a fuller statement explaining why they took the action they did. Whether Blatter would welcome this is another matter. Having been a colleague of one of his "associates" who sorted out the financial fiasco some years ago, I don't trust the bloke.