That sounds an awful lot like an assertion. I'm not going to make any assertions. But what I will say is that until proven with strong evidence, I don't believe aliens exist. Are we going to have a thread on the existence of Unicorns too?
There's forensic paleontological evidence supporting that dinosaurs existed. There's strong forensic anthropological evidence supporting that there were Archaic human beings such as Australopithecus, Homo Erectus, the Neanderthal, and of course Homo Sapians.
There's no physical or strong evidence supporting that aliens, the mothman, Lochness, or big foot exists. Just people claiming to be eye witnesses that have no evidence.
But this is why I don't believe in the existence of aliens. Lack of evidence.