Why should aliens automatically be benign and good?

I don't think they are good or evil, I think they are people/individuals and more than likely, scientists. If they have been here, the aliens were scientists.

Its not really appropriate to attempt to discuss Aliens in terms of good or evil. Those terms have meant different things to different human cultures down the ages and we are all basically wired a similar way.

For example a hive mind society would likely regard an individual life as of utterly no consequence. Feeling free to kill and experiment on individuals with abandon (an idea much used in sci-fi). Such a society could have peaceful intentions to us as a whole at the same time as maltreating individuals. With that type of evolved mind the individual just doesn't count.

That wouldn't make them evil though, just very different and very dangerous.

What if they wish to steer us down a particular evolutionary path as an experiment through alterations to individuals. Like we would breed lower animals to introduce particular traits. Is that evil? We do it to lower life forms...What if the ultimate goal is improvement?

For now I think we'd best be concerned with what their immediate agenda actually is. Once thats known, and assuming its not imminently fatal, the good/bad question will keep philosophers busy for a few centuries....