I see no compelling reason that an alien race would want anything to do with humans. We obviously have nothing to offer in regards to technology. We aren't the dominant or most-successful form of life on the planet (that'd be bacteria). We aren't even the most successful complex life - that'd be insects (the only form of complex life to have survived every single major extinction event).
Frankly, if I were an alien, I'd be saying, "Screw those pesky humans. Go get me some cockroaches and alphaproteobacteria - we can learn something from them!"
Also, why does everyone seem to think that learning about aliens would spark widespread panic? Most people in the world believe that there is life out there, somewhere. And, a good many believe it has already visited us. Given our level of development, we are far more ready to accept that there are aliens here, than say, humanity was ready to accept that the world was round in the 1400s, or the sun was the center of the solar system in the mid 1400s. And neither of those events sparked any panic.
If it were revealed that aliens have been here, it would be a major news story, but it wouldn't make us lose our shit.