It's irrational, really. Not to say that the Golden Gate bridge won't ever get attacked, it may well. But you're far more likely to get killed crossing the road every day, and I doubt you apply the same level of calculation to working out if every road is worth the risk of crossing.

Don't get me wrong, it's totally understandable. I hate to rely on "the terrorists won!" as an argument, but terror is only effective when we allow ourselves to be terrorised by it. If we/politicians/the media applied the same amount of attention to road safety that we do to terrorism we'd all be in self driving cars by now.