The early part (he must have had help, he must have had training, etc.) is not very convincing at all.

It's already been revealed that the shooter was a regular shooter at ranges so there's your training. He's either not heard this or is discounting it for some reason.

Slightly off topic, it is amusing to see people lining up to say this shot is insane (short distance, relatively flat, static target, modern automatic weapon) but when it comes to Oswald (longer distance, more elevation, moving target, bolt-action rifle) it's "Oh of course he could make all those shots".

Anyway, Larry Johnson doesn't seem to be that good at critical thinking. All the stuff about zeroing his scope and how he must have had help, etc. What about he didn't do it (zeroing) and that's why he missed a relatively simple shot from a short distance? Makes more sense.

He seems to draw conclusions from nothing but his feelings.

There could still be more going on, as he gets to later, but I really think if "they" decided to off him they would have made sure they slotted him.