Having definitive proof of extraterrestrial life would change our perspective on how we see the Universe and our place in it. Waking up one day from dead universe into alive universe would be yet another nail in the coffin of religions which build their business model on human desire to be special.
We know very little about the Universe but we already have some understanding of how big it is how some of its laws work. Now, imagine a situation that there's a civilisation out there advanced enough to conquer the vastness of space and break out from the iron fist rule of time just to travel to Earth to crash their spaceship here or, worse, to get randomly captured by species that can barely get their feet off the ground. That idea, to me, is laughable at best.
For that reason I put publications like the one above in my mental library in the same section I store religious publications. I named that section 'Delusions and Wishful Thinking'.