Dont listen to him, gross exaggeration, or inability to see beyond his own nose - I quite agree 50-3 is NOT an average score for everyone. Thats a damn good game for most. I know I'm chuffed to pieces if I put up something like that
How do you know the guy had a wallhack? Was it visibly displayed in the killcam? You do know that auto aim can sometimes 'grab' people through walls? I've benefited from that before, deffo. Also, you could have been crouched in a corner well known for having occupants, so that was the first place he'd look from walking in. Latency could then mean that on his screen he didn't fire immediately, but on yours he did. I'm sorry but I'm becoming ever more convinced that you are mistaking latency for hacking. Hacks very often make themselves VERY apparent in killcams.
Which leads me to my next point - MW3 has theatre. I'd very much like to see a clip of this incident.
Also, believe it or not, despite the massive interest in the online MP facet of this game, the majority buy it for the SP.