question:  Why does the narrator say that the aliens' jokes are dangerous?
context: The most dangerous of weapons is the one you don't know is loaded. Illustrated by Schoenherr The wind howled out of the northwest, blind with snow and barbed with ice crystals. It lit the snow slope to a frozen glare, penciled black shadow down the long furrow, and flashed at the furrow's end on a thing of metal and plastics, an artifact thrown down in the dead wilderness. We got lined up between Earth and Mars, you'll remember, and James pushed the button marked 'Jump'. There was never anything wrong with the Whale till right at the end and even then I doubt if it was the ship itself that fouled things up. Walking, talking natives on a blue sky planet with 1.1 g gravity and a twenty per cent oxygen atmosphere at fifteen p.s.i. The odds against finding Chang on a six-sun survey on the first star jump ever must be up in the googols. We were able to show them our sun, in their telescopes. Look more like cats than people, but they're people all right. When I say they, I mean a ten-man team of them. "Two, they brew a near-beer that's a lot nearer than the canned stuff we had aboard the Whale . Can't say I care for that hot-foot and belly-laugh stuff myself, but tastes differ. People who talk English, drink beer, like jokes and beat me at chess or table-tennis are people for my money, even if they look like tigers in trousers. It was more that we all seemed to make silly mistakes when we played them and that's fatal in chess. Of course it's a screwy situation, playing chess with something that grows its own fur coat, has yellow eyes an inch and a half long and long white whiskers. He was called—well, we called him Charley, and he was the ethnologist, ambassador, contact man, or whatever you like to call him, who came back with us.
output:  The wrong kind of joke could end in catastrophe
options:  The wrong kind of joke could end in catastrophe  It hurts the scientists' reputations to be beat at games like chess  Their practical jokes tend to meddle with spaceship parts  They like to play with weapons and people tend to die