There are a few key differences in how hobbits and dwarves court. These differences can lead to a good deal of confusion, and while Thorin is certainly not the image of a subtle dwarf, Bilbo is still utterly confused about what is going on.
On the way to Kili's birthday celebration, Thorin gets stuck in a massive traffic jam and is understandably furious. He's prepared to do murder by the time a kind man comes to his aid.
They had lived next door to each other for six years. The first year, they didn't notice each other much. The next five, they spent hating each other's guts.