".. this attempt served as a focal point that linked Oswald to the JFK killing." The laughs on them [whoever they are] The Walker incident wasn't revealed until long after Oswald had already been fingered as the assassin.
I don't see a problem here. As soon as the Walker shooting came to light, lone-gunman theorists began to cite it to prove Oswald's alleged propensity for violence and his willingness to shoot someone with a rifle. Just about every pro-WC book every written has cited the Walker shooting as evidence of Oswald's alleged guilt.
All this being said, the documentary does make a few incorrect statements, but it also presents a lot of valuable information.