. . .
Nevertheless, Its not too early to think about the a millennium-long project to visit and colonize the star system. I cannot imagine a bolder step for the evolution of mankind. The project will cost untold trillions of dollars spent across many generations. But it will establish us as an interstellar species, that is for all practical purposes, immortal. This would be an evolutionary step as profound as when Earths first sea creatures ventured onto land.
However, it should not come as any surprise that the people,
Homo sapiens, that exterminated
Homo erectus and the Neanderthals would instill certain reservations within prospective visitors and motivate them to maintain a general ignorance about their existence among that people.
Could intelligent life be there too? Unfortunately, in a lousy coincidence, the star system is too far south to be observed by the powerful Arecibo radio antenna in Puerto Rico, or the new Allen Telescope Array in northern California, that can easily look for any artificial radio transmissions.
Humans are indeed an extremely aggressive species in a number of respects; but I don't believe there is a conspiracy to keep alien visitors hidden from the public. Rather, I think it's more likely that this whole subject (and a few controversial others) are exploited to keep the population distracted - so, a form of population control, if you will.
EDIT: Just noticed you added something else to your answer, and updated accordingly.