Bond is adamant that he is not a sadistic psychopath like Scaramanga and that he only kills other killers, and on government orders, despite Scaramanga's insistence that "we are the same". Throughout the film, though many people die the only person killed by Bond is the killer Scaramanga himself (not quite on government orders, but at least with their approval and foreknowledge), indeed this is probably the lowest body count Bond has in any film. Though he previously told Scaramanga that he would enjoy killing him, when the shot is fired he coldly treats him as just another dead killer.
Scaramanga is right. James Bond is not a spy. He doesn't use cover identities, nor does he stay in one place for years gathering information. His licence is to kill. He's a paid government assassin, first and foremost.(This is basically how a 00 agent is described Casino Royale. The only way to actually get the licence to kill is to murder two men in cold blood without feeling much remorse.) And Dr. No has M threatening to make Bond go back to 'normal duties', which is implied to be the paperwork and intel collection done by regular MI-6 operatives.
To be fair, Bond isn't denying he's a killer; he's denying that he kills for sadistic pleasure.