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.
Also, 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.
How in the hell did M not only know the phone number to Scaramanga's boat, but also that Bond was onboard with both the Solex Agitator and Miss Goodnight?!
Bond and Goodnight actually seemed just as surprised and confused as the audience.
It could be that M had it all along, and indeed, that he already had a lot more information on Scaramanga than he claimed. If so, it would be neither the first time nor the last when M withheld information from Bond. Hell, it wouldn't even be the first piece of information M withheld in this film: He takes Bond off the Gibson case and plays dumb when Bond suggests he kill Scaramanga first; he withholds Lt. Hip's identity and the other use of the Queen Elizabeth until Bond is aboard; and when Bond goes into Red Chinese waters, both he and Bond say M knows nothing of the mission.
It's certainly not beyond believability that MI-6 would use freelancers on occasion.
How in the Hell could Goodnight accidentally press a button with her butt, and not feel the button goosing her ass?
Why does Bond go to all that trouble to get the bullet that killed Bill Fairbanks, when he already has the bullet that was sent to him?
"Well obviously it's useless as a bullet." The Fairbanks bullet was a real bullet used by Scaramanga. The 'trinket' could have been made anywhere.
And it isn't even the calibre Scaramanga uses. It looks like a .32 ACP.
Why don't MI:6 know anything about Scaramanga's appearance? They have a full bio on him and yet they have no clue as to what he looks like (except his third nipple). He used to work in a circus so hundreds of people have seen him (even if it was 20 years ago, that would still tell them that he's six foot tall and thus eliminate, for example, Nick Nack). Even a sketchy description is better than none.
It's hinted M is withholding information from Bond.
As cool as the flying car was, a man of Scaramanga's wealth could just have easily had a real plane or helicopter on standby in that barn.