The evidence for extraterrestrial visitation of Earth is quite solid, IMO. But this does not stop the mainstream scientific community, government, and media from exercising the same kind of arrogant, close-minded, out of hand dismissal that is seen in this thread.
Can you please provide citations for some of this "quite solid" evidence? I'm sure the SETI folks would love to see it--it would save them a lot of wasted time and effort.