When you read the thread title I can imagine you are having serious doubts.
But don't worry, those doubts of yours, I’ll shatter them.

This spoils things that will be shown later in the manga so if you don't want to be spoiled, read this anyway because this is win.

Let me start with giving you some facts from the manga.

Kyuubi attacks Konoha.

Don't believe it, it's all made up.
A lot of ninja died alright, but this made up nine tailed Kyuubi did not do it.

In fact Konoha was at war for some reason.
No details can be given on this war because it was all covered up with this so called "Kyuubi incident" and all information has been erased, but you can take my word on it because it is the Truth.
For some reason they didn't want anyone in the future to know about what happened, so they just made use of the legend of the tailed beasts, which is just folklore.

The Jinchuuriki.

People who host one of these so called Bijuu are called Jinchuuriki.
What do we know of these individuals?

1. They show physical differences (at times).
2. Special powers/abillities, but no bloodline limit.
3. The well known Jinchuuriki were disliked by the villagers.

So we can say they are different from ‘normal’ shinobi

The way Jinchuuriki are treated in the Narutoverse is actually based on history.
In the Middle Ages people believed in demonic possession.
People who were suspected of being possessed by demons were hated/locked up/killed.
Yes, nothing Kishi does is original.

Originally Posted by Wikipedia
Demonic possession, in supernatural belief systems, is a form of spiritual possession whereby certain malevolent extra-dimensional entities, demons, gain control over a mortal person's body, which is then used for an evil or destructive purpose.
In the manga:

Naruto: As soon as he goes 4 tails Kyuubi takes over bit by bit of Naruto, and goes on a wild rampage attacking friend and foe.

Gaara: As soon as he sleeps Shukaku takes over, and directly decides to kill Gamabunta/Naruto when he sees him.

These Jinchuuriki who are said to have demons inside of them are just born with a mental illness similar to Dissociative Identity Disorder.

http://en.wikipedia.org/wiki/Dissoci...ntity_Disorder (In case you don’t know what dissociative identity disorder is)

This form of dissociative identity disorder comes with the possession of extraordinary powers, and is apparently extremely rare.

Originally Posted by Wikipedia
Unlike in channelling or other benign forms of possession, the subject has no control over the possessing entity and so it will persist until forced to leave the victim, usually through a form of exorcism.
These exorcisms were performed by priests or shamans which was ofcourse, much like the Gaible, total fake nonsense.
This is where AL (Pein), Akatsuki's shaman comes into play.

Akatsuki’s scheme

AL uses Fuuin Jutsu: Genryu Kyuu Fuujin to ‘seal’ the demons inside a statue.
Ofcourse there are no demons so what AL does is pure nonsense.
“Fuuin Jutsu: Genryu Kyuu Fuujin” translates to “Sealing Technique: Illusionary Dragon Nine Consuming Seals”.
Yes that’s right, the name of this jutsu doesn’t lie, it’s an Illusionary jutsu, as in “not real”.

You can say this is some kind of Genjutsu almost similar to Itachi’s Tsukiyomi.
It makes the Akatsuki members see nine dragon heads pour from the statue's mouth.
Then it screws up the victim’s mind like Tsukiyomi, but unlike Tsukiyomi it takes 3 actual days in the real world and is way more intense which causes the victim to die from the mind torture.
Now that Pain's face has been shown I really thought he looked like a torture specialist in a way.(Look at nagato)
(Also note that the Rain nin in the chuunin exams used genjutsu)

At this point you will think something like "Why would Akatsuki search for something that doesn't exist?"

I’ll tell you the Truth.
They make everyone including the unaware Akatsuki members believe they are hunting Bijuu.
They use the legend of the tailed beasts to capture the mentally sick Jinchuuriki, and even a mutated crab.
But this is actually a diversion to hide the real objective (Insert one of the many "Tobi=Obito=Madara=Ramen bar owner=Naruto’s Father=Pakkun=Yondaime’s special kunai=Chouji’s bag of potato chips who wants to take over the world by collecting 3 sharingan users" theories here).