Humanity is not prepared for something so monumental as alien contact. Humans have a tendency to fear the unknown. People are also afraid of change and often reject that change. Many people publicly admit to believing in the existence of UFOs. However, many more people refute the belief. Honestly, people would be frightened. Some may even take contact as an act of war.
According to polls by Newsweek and Gallup, 48% of people believe that UFOs are real. The poll by Gallup states that 87% of Americans have heard of UFOs. Just about every culture in the world has reference to strange lights in the sky. Many of those references go back centuries. Even as far back as the bible. Remember the star that lit the way to Jesus?
How many people truly believe in craft that is not from this planet? People have discussed the possibilities of UFOs in depth. However, that does not mean that they believe in the existence. They believe in the possibility of that existence.
Fearing the unknown is a human trait. Only a few people will push the limits of the known world. When they do, they are originally called eccentric'. After they have discovered something of importance, they are recognized as geniuses. However, the label "genius" does not come easily.
What do "they" want? Some people whisper of war. Given the fact that their technology is obviously advanced, they could obliterate the earth before humans could blink. The fact that they have been seen since the dawn of time gave them many opportunities to destroy us. If that was, in fact, their reason for being here. Contrary to movies like Independence Day and War of the Worlds, there would be no happy conclusion for humanity if war were on the agenda. They have been watching us for centuries. They know everything we know, they have seen our movies and know what we would do if they decided to come at us in a malevolent way.
In the end, humans have never been a truly peaceful or understanding race. If there were any form of contact, people would react in a variety of ways. Humans have a basic thought pattern when they are afraid. That thought pattern is flee or fight. We do not know enough about accepting people from other countries to even consider accepting someone from an entirely different planet.
To quote Tommy Lee Jones in the movie, Men In Black, A person is smart. People are dumb, panicky dangerous animals and you know it.' That was his response to Will Smith's Why the big secret? People are smart. They can handle it.' The quote is true in about every possible way.
Humans are not ready to be contacted by anything not of the earth. Maybe, if the world was at peace, maybe then, humanity would be able to handle it. But not before then.