What is Bilbo's reaction to Thorin's speech? Chapter 12

Bilbo is rather defiant after Thorin's brief speech. He seems to feel as if he's being taken advantage of.

"If you mean you think it is my job to go into the secret passage first, O Thorin Thrain's son Oakenshield, may your beard grow ever longer," he said crossly, "say so at once and have done! I might refuse. I have got you out of two messes already, which were hardly in the original bargain, so that I am, I think, already owed some reward. But ‘third time pays for all' as my father used to say, and somehow I don't think I shall refuse. Perhaps I have begun to trust my luck more than I used to in the old days" - he meant last spring before he left his own house, but it seemed centuries ago - "but anyway I think I will go and have a peep at once and get it over. Now who is coming with me?"