Sadly, the human race is not ready to handle the concept of life on other planets. We can’t even accept that other life forms on this planet have any intelligence or feelings, let alone life forms form another planet. If ET was to make a first contact tomorrow, the world would still go on as before, and the aliens would be treated like animals or hoaxes. Any messages they have for us would be ignored.
If ET does exist, then he, she or it would most likely be intelligent enough to know that they would be in grave danger if they made themselves known to the general human population. And besides, they might have absolutely no interest in people. Perhaps they are more concerned with talking to guinea pigs. Guinea pigs certainly make more sensible conversation than most people, anyway.
If ET did come out of the universal closet (so to speak), they would most likely be screamed at to go back where they came from. They would be seen as trying to take over the jobs, resources and daughters of God-fearing Americans (or whatever country they would land in). They would be laughed at for not speaking the language properly, be sent to jail and have their vehicles impounded.
The reason for this anger at another being of superior intelligence is not just because our own stupidity. Imagine if you suddenly discovered that you had a guardian angel and was able to have a face to face meeting with him, her or it. You would most likely remember all of the times you were robbed, assaulted, contracted a painful illness or worse. And this angel just sat back, watched, knew what was going on and did nothing to relieve our suffering? If I ever meet my guardian angel, the first thing I would do is punch him right in the nose.
If ET was to come out of the closet, they would have to come very humbly and appear somewhat crippled. Perhaps they should admit that they stole their spacecraft and have no idea how it works, but are ready to sell it in order to get a bite to eat (or absorb or whatever) and a large vial of quality Earth drugs. We would be a lot more sympathetic to them, because we could relate.
