It is of course well known that careless talk costs lives, but the full scale of the problem is not always appreciated.

For instance, at the very moment that Arthur said ”I seem to be having tremendous difficulty with my lifestyle,” a freak wormhole opened up in the fabric of the space-time continuum and carried his words far far back in time across almost infinite reaches of space to a distant Galaxy where strange and warlike beings were poised on the brink of frightful interstellar battle.

The two opposing leaders were meeting for the last time.

A dreadful silence fell across the conference table as the commander of the Vl’hurgs, resplendent in his black jewelled battle shorts, gazed levelly at the G’Gugvuntt leader squatting opposite him in a cloud of green sweet-smelling steam, and, with a million sleek and horribly beweaponed star cruisers poised to unleash electric death at his single word of command, challenged the vile creature to take back what it had said about his mother.

The creature stirred in his sickly broiling vapour, and at that very moment the words I seem to be having tremendous difficulty with my lifestyle drifted across the conference table.

Unfortunately, in the Vl’hurg tongue this was the most dreadful insult imaginable, and there was nothing for it but to wage terrible war for centuries.

Eventually of course, after their Galaxy had been decimated over a few thousand years, it was realized that the whole thing had been a ghastly mistake, and so the two opposing battle fleets settled their few remaining differences in order to launch a joint attack on our own Galaxy – now positively identified as the source of the offending remark.

For thousands more years the mighty ships tore across the empty wastes of space and finally dived screaming on to the first planet they came across – which happened to be the Earth – where due to a terrible miscalculation of scale the entire battle fleet was accidentally swallowed by a small dog.

-- Douglas Adams, The Hitchhiker's Guide To The Galaxy

That reminds drag of Halo, though significantly more silly.

In Halo, the Covenant are on an interstellar crusade for holy artifacts left behind by the Forerunners. When they discovered the planet Harvest, inhabited by humans, they saw tons of artifacts on their scanners. So naturally, they landed on the planet and started blasting the humans to steal the artifacts. But the more humans they killed, the more artifacts disappeared from their monitors. The humans must be destroying the artifacts out of petty spite! What heresy!

The Prophet of Truth is curious about what kind of artifacts the humans have, so he goes to talk to an ancient Forerunner AI they have in storage, Mendicant Bias. Truth shows Bias the symbol that they keep seeing on human worlds. Bias says "You fool, you've got it upside down. Turn it around, see? It says Reclaimer. It means a person the Forerunners have chosen to inherit their empire. You've just been killing these humans? No wonder the reclaimers keep disappearing, you're the one who's doing it!"

So Truth realises that he's been ordering his troops to kill what should rightfully be considered demigods by his religion, and who he should be worshipping. And he realises that if he reveals this information to the people, he and the other Prophets will lose all their political power since there are Actual Fucking Gods walking around. So naturally, Truth declares a Holy Genocide against humanity so that nobody will ever figure out that he's guilty of Deicide and that their entire religious political structure is a lie.

Or, you just decided on first contact, but, suddenly, ship goes boom after being struck in the propulsion system with a bullet like manhole cover.