Another consideration...
While I think we can all agree that a hoax/propaganda campaign about ufo's would likely be exposed at some point, it would be the public nature of such a hoax that would increase that likelihood. But I think we can also agree that there are many top secret projects which are completely unknown. Projects that are not part of some disinformation campaign involving the public, but real advanced military research completely hidden not just from the public but also from the rest of the military complex. Need-to-know-basis stuff. Perhaps highly advanced quantum entanglement experiments. Whatever. If this is not a hoax or natural phenomenon, it is either something we are doing or something aliens are doing. The former has to be more likely.