I'm not trying to come down on you, since you're playing devil's advocate, so any

attitude you get from me is directed elsewhere.
Yes, it's an extraordinary claim. The technology it would take to traverse the universe (or just a galaxy) is mindboggling. A being
that far technologically advanced has no need to come here. I mean, would Bill Gates land his helicopter at RadioShack? If these beings have
mastered interstellar travel for crying out loud, they can easily observe earth without us knowing. Have a little camera that looks and acts like a bird or something, you know? Hell, have an invisible ship float directly over a city and look down with binoculars. If aliens able to fly here from millions of
light years away didn't want to be seen, we wouldn't see them. If they wanted to be seen, we'd know already. With all of our satellites and radio signals and the massive amount of stuff being transmitted over the frequencies, aliens wouldn't even have to come NEAR us to learn everything about us.
When explorers left Europe and found America - and found people already living there - what did they do? They made contact. They didn't hide in their ships and sneak ashore to flatten circles in the natives' corn fields. They established contact, and then proceeded to kill them and take their stuff.
Granted, these are
human motivations, and it is a small possibility that aliens
would travel across vast expanses to simply scare some pilots and butt-rape a few rednecks. ...but I don't think so. If aliens were here, we'd know.