The evidence is available -- video, ground-based photographs, NASA footage, testimonials, reverse-engineered technology. Mired in silliness, hoaxes, and government deception aimed at discrediting legitimate sources, credible proof of the existence of extraterrestrials is readily available.
Whistle blowers come forward, former government officials come forward, private contractors come forward, there's no shortage of evidence. No one has to wait for CNN or any other corporate network to say what is and isn't okay to believe. (PBS is no better, finding itself in the pockets of as many corporate sponsors as Fox News).
What Buddhist evidence is there? If there were no UFO beings (devas) watching from above and descending or reptilians (nagas) living underground and exerting undue influence on human affairs (as movers and shakers offering governments power at least since the time of the Vedas and the Sumerians) then there's something to explain: Why did the historical Buddha constantly refer to them?
From his time down to the present, temples around the world chant the "sharing of merits" to benefit unseen beings of various groups, whether benevolent or malevolent to humans as suits them.
SHARING MERIT (daily recitation)
"May beings who inhabit space and Earth, devas (shining ones) and nagas (serpent beings) of great power, after having rejoiced [and thereby shared] in the merit, long protect the Buddha's dispensation." (Akasattha ca bhummattha deva naga mahiddhika punnantam anumoditva ciram rakkhantu loka sasanam). This chant as well as countless sutras reference them.
Of course no proof is good enough. We disbelieve because we choose to, not due to a lack of evidence. And there are consequences for our choice. We think ignorance is the way to a comfortable life. But wisdom is the way to freedom, happiness, and the good of all.