I can not recall how many times I've heard a scientist or skeptic on TV say something along the line of "A highly advanced alien race would probably regard humans as nothing, but insects. (sometimes cattle)" Likewise I can not tell you how much I disagree with that. Wait, I can!
Human history is riddled with "civilized" humans encountering other humans that we often consider "savage" or uncultured. For the most part we also disrespected many of these cultures by forcing our beliefs on them or enslaving them. And while today there are some groups and individuals who would still prefer to do the above, we have more regard for cultures that aren't part of the "modern world". In fact we are more curious about them then anything else, but at the same time hesitant to contact them for their good and ours. (Exposure to our diseases which isolated tribes have no immunity to can wipe them out. Some of these tribes aren't exactly the most friendly to outsiders either.)
I feel that an extra-terrestrial culture would probably react to us in one of the many ways mentioned above. If our history as a civilized species in full of it, an E.T. civilization would probably be as well, both the good and bad elements. That also means that they'd probably recognize us as being intelligent (at least to an extent) and would either try to communicate with us (for good or bad) or leave us alone for reasons they view as being good. However, until we have open and regular communication with an E.T. society, the best way to study how one would behave is to study ourselves.
Some related reading/examples:
Incredible pictures of one of Earth's last uncontacted tribes - Daily Mail Online
Article about the same tribe - BBC News
Wikipedia on slavery
Native American Timeline of Events