Those things called UFOs (for good reason I might add) MUST reach a level of true evidential support in order for willful ignorance to come into play. At that point one could be accused of willfully ignoring what is an established fact concerning UFOs. Just ignoring the reasoning for your hypothetical argument constituting UFOs as ET spaceships is called one's prerogative. That's because, again, we are NOT dealing in absolutes but rather solely a speculative consideration upon which MANY hypothetical arguments may relate and apply to. That is until one argument, or none of them, are found to be factual based on the successful discovery of what UFOs actually are. Then, and ONLY then, will UFOs no longer be Unidentified or referred to as "UFOs". At that point UFOs will be referred to for what they actually are. Possibly they are spaceships, possibly time machines, or possibly that which we have never even conceived of yet.