Yes, they're suggesting that bridge building isn't adversarial. In bridge building you might often ignore questions like "what if that nearby skyscraper fell o

Yes, they're suggesting that bridge building isn't adversarial. In bridge building you might often ignore questions like "what if that nearby skyscraper fell on the bridge" or "what if there was a 100-year flood every day for a week". They're scenarios that can conceivably happen but they're very unlikely. In computer security, you wouldn't be so safe because you need to protect your digital bridge from an adversary who has no problems demolishing the nearby figurative skyscraper. Of course there are real-world situations where bridge building is adversarial, if you're in a war-zone for instance. I think the author is discussing more civil situations like "should we spend an extra $1B to make the bridge asteroid proof".