Billy eyes Vasquez after a moment, turning away to take another long drink from the bottle of alcohol they have. He wishes he had cigarettes, something else to fill his time with as he gathers together what he wants to say. The points Vasquez makes are valid, but unnecessary; Goodnight and Billy had this discussion many times, during their numerous close calls. But beyond that--

"You're making many assumptions about what our relationship was." and nothing Billy says betrays the truth, instead chiding and dismissive of having implications and hidden meaning thrown at him. Either Vasquez makes his statements in full or not at all because Billy won't answer them any other way.