This could be a short story/novella/novelette; I don't remember. SPOILERS!!! I don't know how to describe this story without them. It begins with a discussion on the bridge of a spaceship approaching a planet. The two beings are worried about the war and about asking the beings on the planet to come help. The planet has been under lock-down for quite some time ever since the galactic federation realized how dangerous they could be. Letting them free to help in this war is a last resort. The landing party contacts a family and is trying to judge whether these beings are as dangerous, vicious and warlike as they once were, or if they have actually become as peaceful as the bucolic landscape seems to indicate. One of the junior officers goes exploring and discovers that the planet's inhabitants have created an incredibly large computer complex below ground that links all the people (even the animals, I think) so they can speak to each other mentally. The landing party slowly decides that the help is worth the risk, which seems not as bad as they had feared, so they authorize removing the barrier around the planet. Ultimately, the reader's suspicions are confirmed: the planet is Earth, and we are the most dangerous beings in the galaxy. I read this at least 20 years ago; could be as much as 40 years. Very likely in Fantasy and Science Fiction mag, Galaxy, or Analog. I'm pretty sure it was not a novel. I hope someone recognizes it. Thanks for reading!