Why dean to throw a necklace--Supernatural

In Supernatural Season 8 , This season there are many supernatural desperate moments. Sam and dean parted ways, bobby was paralyzed, colt gun can not kill Lucifer, Allen and jo die, bobby wanted to commit suicide and so on. But perhaps the saddest moment in the "Dark Side of the Moon", when the dean amulet necklace when thrown away. (We are all heartbroken)
If you do not understand the previous story, the details may be insignificant, but it's really important. This necklace is ready to give young sam had their father, and ultimately sam necklace as a Christmas gift for the dean, this necklace is the bond between the two of them, is the dean sam always as surrogate father and protector of proof. Threw a necklace, dean also cut his and Sam's custodial loop.
Why does he do this? We have seen two brothers against each other, and even parted ways, but dean is always wearing a necklace. Why, there are two possible explanations:
1.dean hate sam
Obviously, this is impossible. But if we follow this logic, in heaven, dean sam seen all the best memories of those moments sam leave the family, it was his nightmare. Some people might say that the realism of the transferee to the family sam dean realized he wasted his life time to take care sam, and get in return is sam always wanted to leave his family.
If you believe this, I am you may be Brooklyn, totally do not understand the meaning of family. The truth is you can not stop loving your family. Dean may not bear the sight of his brother, he and his brother might have earned run, but he always loved him. So why he would throw his brother had given him the most precious gift?
2.dean are preparing for their sacrifice
It is obvious dean has come to the verge of despair. In this whole season he are trying to find ways to fight with Lucifer faint hope. Originally colt gun, then is God. In the "My Bloody Valentine" This sets the last dean tearfully prayed to God for help because he could not stop the apocalypse independent.
And Joshua in the garden of paradise conversation so that he completely awake. Dean found his last hope is the only chance to get help, but completely useless. In addition to more desperate, dean has realized that it is ready for his only way out of the time, that is to say on Michael "yes".
It is really a very simple reason. Dean has tried all possible options have failed, so now Michael said "yes" has been the only visible option. He may not admit it, he did not even know that they have made this decision, but this is the only explanation why he threw the necklace.more dvd:True Blood Season 5 DVD
Michael if he knew he would say "yes", then he may have to kill his only brother, dean the only way to avoid doing this is to first pushed his brother. He tried and sam emotionally alienated, so that he can be strong enough against Michael said "yes". This is the only way