At what point in time and under what conditions did these officers make the statements that you are basing your claims on?
He's going to try and "deconstruct" the evidence and make the revolver disappear. But he won't give an alternate explanation for the existence of this revolver; he won't explain how it came to be in the possession of the police; he won't explain how the police got the actual revolver that was used to shoot Tippit. The shells recovered by eyewitnesses as the scene (from places AWAY from the direct location of the shooting (by Tippit's car); that dismisses the "gun was an automatic" argument) - many of whom say the gunman was Oswald - were fired from that revolver. If it wasn't Oswald then how did the police acquire that revolver?
Again: how did they get that revolver?
He won't answer any of this. He can't. He's trapped himself in his defense of Oswald so that he cannot offer any alternative explanations. Because his approach in defending Oswald - making the evidence disappear - makes him unable with any intellectual consistency to argue for an alternative. Because the evidence for that too must disappear. He's made the revolver and rifle and other evidence disappear and he can't without being exposed for being a conspiracy believer (which he denies) provide one.
Meanwhile, he'll be silent about all sorts of bizarre conspiracy claims like the recent ones involving Ruth Paine. He critically challenges Tracy's examination of the claims but NOT the actual claims. The person making the claims about Paine being some sort of CIA asset or conspirator goes unchallenged.
Lots of other people have tried reasoning with him. They all failed. It's best to move on from this type of conspiracy mindset. You cannot reason with it. I don't know what these people are doing; but it's a big internet and you come across all sorts of things. This is an example of it.
At least the conspiracy believers - who say they are such people - are consistent. Their explanations are absurd, they involve planning and coordination of dozens of people -including civilians. There is no evidence for such planning. It's all supposition and fantasies. But they make them anyway. They don't run when asked for an explanation.