1. Because Balthazar considers Castiel to be his brother.

2. Because Balthazar gave up the most powerful arsenal in the world to him, expecting nothing in return.

3. Because Balthazar was the first one to point out that they were betraying Castiel.

4. Because, "I grieved your death!"

5. Because for Balthazar he'll always be Cassy.

6. Because Balthazar used Lot's Salt on Raphael to save Castiel.

7. Because they went up against one of the Sisters of Fate together.

8. Because Balthazar unsunk the Titanic to help Castiel.

9. Because Castiel thought Balthazar was impetuous but still cared for him.

10. Because...