Interesting thread. I would just challenge the assumption that if technologically advanced aliens came near us, they would fell compelled to attack. Basically, there are only three reasons why one group of beings attacks another:
1) Because they feel those beings are a threat to them. Because we have not yet achieved the ability to travel freely through space, time, or other dimensions, we are not a threat in that regard.
2) Because they want to take something the other group possesses (material goods, natural resources, land, slave labor, etc.). But, that only happens in a closed-end system, where there is a finite amount of "X" available. Why do we not see people on earth fighting over air? We all need it to survive, but from out perspective there is an unlimited supply available to us, so we don't fight over it. Instead we go to war over energy. Suppose there were an unlimited supply of freely available energy? Suppose there were Star Trek-type replicators that could supply everything we might need or desire? If you had that sort of technology, where you could rearrange matter on the molecular level to create anything you want, you wouldn't need to attack anyone (you might also be regarded as a deity, should you choose to use your technology to impress those who do not have access to it - look up "cargo cults"). And that brings us to...
3) Religion. The most irrational reason one group of beings attacks another, yet historically one of the most frequent. Of course, this is often combined with one of the motivations in 1) or 2) - people seldom care if some faraway group has strange beliefs or practices if they don't see that group as a threat, or want to take something they possess. Native Americans and African Blacks were portrayed as heathen savages, when other people wanted something they possessed (land, human energy). In the case of Native Americans at least, many Americans now realize that their spiritual practices had great value (at least those parts that didn't involving harming others). Funny how a group stops being "heathen" when you no longer are interested in anything they have.
The most common reasons I hear for UFO incursions is that some aliens are interested in protecting us (they see us as their genetic offspring, or at least relations) while others want something we have (genetic material, the most frequent reason cited for "alien abductions"). The problem UFO non-believers have is that there is a growing body of evidence, including photographic and video evidence, that UFO's exist (however, proof of existence does NOT prove origin - they might be entirely of terrestrial origin, although that of itself should have us asking what kind of energy source and propulsion methods they are using that we're not being told about). The problem UFO believers have is that you can't prove where these object originate (there is growing thought that they may be inter-dimensional craft, which might explain why they appear to violate our laws of physics by making impossible high-speed turns) and that there are so many sometimes conflicting stories, some of which are obviously wrong (and some of which were obviously written to sell a book).
For those interested in the topic, one book I read a while back (during an Internet connectivity outage when I had absolutely nothing else to do) that I thought was interesting was "The Day After Roswell" (author's last name was Corso, I'm too lazy to go look it up right now). If you believe his story, we have definitely been visited by beings not of our planet and the government is covering it up, so as not to panic the population and destabilize society. But others have suggested a more sinister motive - to protect the big oil industry, since the wreckage we have obtained has contained sources of energy that are far better than what can be obtained by burning oil and coal (the guy that runs "The Disclosure Project" seems quite interested in this aspect of it).
I'm not sure what to believe, since I've never personally seen a UFO, nor for that matter do I know anyone who has. But then again, I've never been to Paris, but I believe that the Eiffel Tower exists. And a lot of people hold religious beliefs that are based on far less objective evidence than what we have for the existence of UFOs, and we don't make fun of them or giggle when they talk about what they believe (well, most of us don't). I'm not persuaded one way or the other, but if UFO's ever do land, I'm not going to buy the first story they tell us about why they are here (if we can't trust our own people to tell the truth, why on earth would we believe what an alien being tells us)? And if they are smart, they should know we're not going to trust them, and that may be one reason they haven't shown themselves more openly.
