A suggestion:
If anyone has time, find and read a book called "The Killking Star", by Charles Pellegrino and George Zebrowski.
Interesting scenario listed that gives a (I think) plausible reason for alient hostility. Also highlights some of the technical reasons why a huge difference in technology may not make that much difference (especially when looking at vehicles capable of traveling a signifigant (10%+) percentage of lightspeed). We actually aren't too far from the capability to create relativistic craft using antimatter as fuel. We have the technology now to create a simple craft, we can make antimatter, the remaining hurdles are crating a magnetic "nozzle" for the engine and the political and social will for such a project.
For perspective, an object of a few hundred tons (relatively small for an interstellar craft, at least in desings we currently believe plausible) entering an atmosphere (or contacting any matter) at a signifigant percentage of c would sterilize a hemisphere, more or less. To the bacterial level.
In any case, the biook includes a chapter or two of transcripts that occurred between various scientific and government agencies concerning what might be known about any extraterrestrial intelligence, without ever haveing met them or knowing the conditions of thier evolution.
I don't believe there's a higher chance of benevolent aliens than hostile, although I don't think hostile is mnore likely, either. Personally, I believe that the primary focus would be uncaring, especially if they are more advanced than us. I'd see a situation similar to today, where we clear wilderness areas for housing, development, farms, or whatever...and don't give too much thought to the animals or other lifeforms we kill. Even species closer to us in intelligence, such as chimpanzees, some of the great apes, or dolphins, are hunted for sport, eaten, or simply killed through carelessness without much thought. I think we'd most likely be an interesting curiosity, until the alien Zik`sirth`fgnsdjkl-t decided we taste good, or our pelts look nice on the wall, or that human spleens make an excellent aphrodesiac, or that Earth would be a great spot for their new "ExoDisney" theme park.
And all the flower-and-peace, happy-zippity-do-da about any race advanced enough for travel being moral and such? Show me evidence. Show me that our morality has grown with our technology, in any way. The only thing we've done is extend the sizes of our tribes, and any aliens would, by definition, be outside our tribe. Someone earlier mentioned the exponential progress of technology...yet evolution still proceeds slowly. Our technological capability has already outpaced the evolutionary biological changes that our early days brought on for survival, such as male aggression or a preference for sugar and fat.
I know this sounds cynical, but I'm really not. I just don't believe that anyone can make any sound judgement about the motivations of any alien race that might or might not exist. I wouldn't bet money on then either being benevolent or peaceful, or hostile and warlike. Personally, I think the best way to greet any alien race we encounter is with open arms, and a large gun hidden close at hand. Depending on the way things go, you give then a hug or reach for the gun. But that's just me
Also, even if this alien race is highly evolved and benevolent and peaceful, why do we expect their intraracial peace to extend to us? Especially if they view our behavior as savage, a bunch or warlike hairy apes? Might they not consider it best for all involved if we were not allowed to spread?