Why would aliens be concerned with attacking our world when there are far more resources available in a far more accessible places?
Also, is it not possible that there is some selective pressure towards compassion? After all, the Drake Equation suggests not one but thousands or tens of thousands of alien entities. If this is correct, there is already an existent culture of interacting groups. In such a group, aggressive, violent life forms would be co-cooperatively destroyed by others who vastly outnumber them, and peaceful ones would be accepted in, strengthening this federation, erm, republic... well... my point is, if there is one alien, there are almost certainly many aliens; and if there are many aliens, ones that aggressively strike out in a many-fronted war will quickly loose out. So, good news for us is that if there is alien life, it's already pretty co-operative and benevolent.
I for one suspect that intelligent life is far less common than we think it is. I think that the jump from subcellular to cellular is a very big step and may only happen incredibly rarely where the right combination of tide pools, chemicals, radiation... exist to make it useful. Similarly, multicellular life forms are also at a disadvantage compared to single-cells especially in highly unstable climates like we expect to find often in the galaxy. And the leap from small to large, and above all, the leap from sapience to sentience. We like to think that we humans have a great advantage, but we are far from the masters of this planet. It would be more accurate to call this world Bugworld, as insects have a far greater influence on the ecology than we do, and are more likely to survive any cataclysm.
I think that as (if) we explore the universe, we will find a great deal of planets that are almost alive, with surfaces covered in viruses and crude photosynthesizing gels, and we will find a smattering of planets more complex that have microbiospheres but not true multicellular (or at least macrocellular) life, and again a fraction- a tiny fraction- of those may have animals and plants that we would recognize, or perhaps some other distinction, and we might, somewhere, find some life that is in some way tool-using and intelligent. However, just as with the hard climb up the tree of life, I don't expect many aliens to have experienced the industrialization that humanity did. There was no force that drives humans to invent, and for the vast majority of our history, we remained at a very steady level of technology, sticking to what worked. I don't expect aliens to be any faster.
For this reason, I don't think it's too extraordinary to suggest that we may be the first intelligent, space-faring life in our local area. After all, that's what the only concrete evidence we have suggests...