As a species, I believe we have much to offer. If another species were to visit our planet they would have to be more evolved and intelligent than we are in some form to have traveled possibly light years to get here. A human beings we have much to give to other worlds. It bogs the imagination to even conceive another life form. What would they look like? Would they be flesh or would they be translucent? Would they eat food like we do, or would they exist on another type of fuel? Food is fuel for us and may not be for another species.
I believe if another planet were able to support a living being, regardless of it's form, it is quite possible that it would die from disease or virus if it visited our planet and visa versa. We have organisms living all around us on this planet. They live in our food, our beds and our air. Maybe we are the aliens here, giants, so to speak and the viruses are the inhabitants?
The "what ifs" make for good conversation though and I am somewhat of a Science Fiction lover, so anything about UFO's is exciting. But, are we ready for UFO's? I don't think now is a good time. My husband just started a new job and so have I. We haven't had an opportunity to get established with all these changes without adding an alien species to the mix. I am afraid he would get out the shotgun if an alien came to the door, especially if it were big and ugly.
After all, God came to Earth once and look what happened to him. He was for all practical purposes an alien in this world. He even looked like a human being, but as soon as he started showing off some of his powers, he was brutally murdered. I do not believe that if God came to Earth again, it would be any different. The funny thing about Man is he truthfully doesn't like change unless he is the one who decides to change.
There may come a day when a UFO appears in the sky and every man will see it, so there won't be any reason to hide it or conceal it in any Area 51. It will be there for all to see. It will land and we will hear a voice, "Please place all your weapons on the ground, or you will be terminated".