"explanation for most UFO incidents would seem to have terrestrial explanations"

The thing is, the most recent reports released by the government, (which I believe the person you are replying to is referring to), stated that while (something like) 98% of UFO reports did have plausible terrestrial explanations, (something like) 2% of them had none. With even the most rare explanations being discounted by leading experts at NASA, the Pentagon, etc.

That is the new piece of information that has revitalized the discourse. I'm a skeptic, but I am personally still waiting to hear the rational counter­-argument to that particular point, that can bring us back to Occam, so to speak.