I have always wondered why Azog likes to refer to dwarves as scum, but after The Desolation of Smaug I can sort of understand why. The leader of the company, seems to me a reckless, deceitful, angry dwarf of little intelligence, full of ambition and limited means.
First, Thorin couldn't open the door to Erebor and almost gave up and left Bilbo to open the secret entrance. This shows that he is not an intelligent person, having risked the lives of his men just to fail in the end.
Second, Thorin deceived the master of Lake-town with the promise of riches, and in an act of goodwill, the Master allowed Thorin's men a way through. If Thorin fails to kill the dragon, the lake people will suffer the consequences.
What is baffling is that the company of dwarves keeps taking orders from Thorin, having put the lake people at the mercy of an angry dragon. Why do the company of the dwarves keep on believing in the leadership of Thorin?