I hope I can help point the way to some answers for you. I sense the frustration that you must feel. The questions you pose are very good and you are not alone in asking for the answers.
A cool website about UFO's and Conspiracy etc. had the items coded for how credible the "historical" incident was. These timelines can be found from several sources and are generally strict enough for the skeptics. Many movies have been made about UFO's in Art and History. Archeological finds are subject to interpretation and interpretation is subject to the guilletine. Even so, some have stuck their necks out to present astonishing theories backed up by lifetimes of study and research by accredited (and some discredited) scientists and intellectuals. Hundreds of top notch witnesses have made statements to the national press club (see You tube) about their involvement and experiences with UFO's, government coverups and such. Every day now there are new pictures and video recordings of new UFO's and Crop Circles, even Alien's and many unknown creatures as well as abductions, and cattle mutilations. Keeping it quiet? Hardly! (If you think the Newspaper and the TV are giving you the real news, then yes, it's quiet out there, nothing to see here folks, clear the area.)
Humans have been evolving for perhaps millions of years (five or so some scientists surmise), civilisations may have had time to rise flourish and fall victim to natural events on a planetry scale. We know that if our world suffered a planetary disaster that all trace of our existance could be erased in a short time. What is time to the universe? We sit somewhere perhaps 10 billion years out from the galactic core, and there is another 5 billion years of stars towards the edge of the galaxy on the other side of the milky way. The point here is that we don't really know about all of earth's history or the entire history of humanity. An advanced civilisation such as the legendary Atlantis could certainly have flourished with open celebration and full knowledge of ET's.
Fun fireworks. How about the famous Nuernburg UFO wood cutting? Nuremberg Germany UFO Battle (1561)
That must have been some battle to see live!
Lately though there is a story about a little shindig up in the arctic where the humans got served their own butts, but I have seen zero proof of the battle. If the battle takes place in space it is out of view from this pond. How do two extra terrestrial zoo directors fight? I hope they are beyond killing other sentient creatures but there are supposedly more than one species in the area, and each species is subject to it's individual's agenda.
I don't see that anyone would panic (on hearing the disclosure) any more than we panic over knowing that Muslim terroists want to see us all dead is panicing anyone. I think a visit by relatives strikes more fear and panic into hearts than the president saying "we haven't been exactly truthful to our voters". I know my friends in L.A. will only wonder how that will affect their morning jog to the Latte' shop. The News had better not disrupt normal programming! I won't be shocked or upset, nor will at least 25% to as many as 56% (some survey's) of those who feel there is a hidden truth, we are being visited. There just hasn't been enough of a reason for anyone to commit suicide over the matter, the opposite is the case. Each of us who knows should help the rest to find the truth if that is their goal. We can only point the way others must have their eyes willingly open.
If the stories are true about humans being like lab rats or exibits in a biological experiment then our only hope to break free is to first acknowlege our prison. Unfortunately our prison is built on human ignorance, greed, hate, emotion. Until we can transcend and grow spritiually we will be trapped fighting for scraps in the dirt.