None of those things are infallible. Bias can push a conclusion in any direction.
True. The evidence can be wrong. The photographic analysis, the handwriting analysis, the fingerprints. Certainly the eyewitnesses, something we all know can be terribly wrong. But one must show where they are wrong. Simply dismissing them out of hand is not how one reasons.
And to dismiss all of the evidence against Oswald? Every single piece? Unless, again, the goal is to defend Oswald at any cost.
At some point - it's been more than fifty years - judgments have to be made. We sift the evidence, weigh it, consider alternative explanations and come to conclusions. This incessant "No, no, no" is not how reasonable people consider things.