Continuity mistake: Patricia Neal is in flats as she runs across the field to give Gort the message. When Gort picks her up, she's in heels.
Character mistake: At the beginning of the film, the British radar-man says it's moving at 4,000 mph. Then says it must be a Buzzbomb. As a British radar man, he'd know that the Buzzbomb, or V1 rocket, only flew at 360 mph - 75% were shot down by the RAF.
Continuity mistake: At the end when the spaceship is about to take off the people rush away from their chairs in fear of the launch. After the ship launches there are no chairs anywhere on the field, just the people.
Revealing mistake: After Gort takes out the guards and Carpenter passes by him, Gort turns around to follow, and the zipper for the costume is visible.
Other mistake: As the UFO approaches and flies over the park, the camera pans to the right with the UFO in the upper left corner of the shot, tracking it. As it does, the UFO passes over the heads of two women, who are gazing at a spot behind where the UFO is when they should be turning their heads to the right, watching the descent.
Continuity mistake: After the power comes back on, a newspaper front page has Klaatu pictured with the president standing just outside the entrance to the saucer's dome, and Gort standing about five feet in front of Klaatu in the same place. But early in the film, Klaatu was on the ground with the president, and Gort never preceded Klaatu coming out of the saucer.
Answer: They said, how they handle their earth problems is no concern to them, it's only if they bring it to outer space and other worlds, they would take drastic measures to ensure that did not happen.