1) The evidence is OVERWHELMING that Oswald shot Kennedy.
2) It is IMPOSSIBLE to prove that Oswald acted alone, even if he did.
3) Given 1) and 2), the burden of proof is on the conspiracy theorists to show who the other people in the conspiracy were. At this, they have failed, and reasonable people need not listen to them until they come up with some positive evidence involving PEOPLE WITH NAMES. Otherwise, NOTHING FOLLOWS from their efforts.
There are many mysteries in history, the details of which we are unlikely ever to know. Should we just stop wondering about them?
In this particular case, a confirmation that JFK was the victim of a conspiracy would have immense consequences. So, even though the chances of learning the truth are vanishingly small, I think it is worthwhile to at least keep a small sliver of doubt about the "official" version of events alive.
I believe in Occam's Razor for narrowing down the possible explanations of most natural events - but this was not a "natural event": it was the product of human will and human action. As such, it is permissible to "multiply possibilities" a little.
Convicted killer and LBJ hitman Mac Wallace's fingerprint was found in the sniper's nest.