If the ETH is correct, and ET is visiting Earth, are they good (as the Contactees suggested), or evil (like this space vampire, which is menacing Erin Gray's Colonel Wilma Deering)?
It is a question that continues to be bandied back and forth by some UFO researchers.
Now, you'll sometimes hear a ufologist who favours the "good guy" theory state that for the aliens to have reached the level of technology that would allow them to travel the stars, they must have learned how to deal peacefully with all their problems, or else they would have destroyed themselves. I've heard Stan Friedman touch upon this idea in lectures, for example.
This makes little sense to me, given our own experience. After all, we have developed lots of things that we could use to destroy ourselves (nuclear weapons, biological warfare, reality television), and yet we're still here and moving forward (whether that's forward in a positive or negative way is up to each individual to determine).
The real answer to the question of "what the aliens might be doing here" is:
The one thing you can be sure of, however, is that when a ufologist talks about reasons why ET is coming here, he or she is really talking about what they hope are the reasons for ET visiting.
Optimists will see the good; pessimists will see the bad.
Thus, the Contactees, who lived under the shadow of the mushroom cloud, believed ET to be a benign presence, here to help us through turbulent times. Conversely, ever since Vietnam and Watergate, the aliens are more likely to be portrayed as bad, usually tied into some government conspiracy.
As far as I'm concerned, trying to assign motives to ET (whether they are coming here or not) is like trying to assign human motives to God. It is a fruitless exercise that says more about us than them.
While this may be interesting to psychologists, it is of little use to the investigation of the UFO phenomenon.