"I got five hundred from your father, which I didn't ask for, but he can afford to give it to me. I can get another thousand for finding Mr. Rusty, if I could find him. Now you offer me fifteen grand. That makes me a big shot. […] What are you offering it to me for? Can I go on being a son of a b****, or do I have to become a gentleman?" (32.57)
Vivian tries to buy Marlowe's silence by offering him fifteen grand, but at the same time she also calls him "a son of a b****." Marlowe sarcastically points out that her motives, not his, are morally suspect. He has no intention of accepting any money, and sarcastically lists all the reasons why he's such a "son of a b****." But this list reveals that Marlowe has only been working in the General's own best interests, and that in fact all of his actions have been "gentlemanly" and morally upright.