Comments like this about the remoteness of the risk always carry the implicit argument that one should not pay attention to it because of the low probability. It's certainly irrational to think there's a high probability of it happening to you, but it's eminently rational for stakeholders like movie theater operators to minimize the risk - after all, to the extent that customers consider the showing of the picture to be a risk factor, they're going to stay away from the entire theater even if it is showing other pictures they might want to see.

There are more civil ways to express that.

There are more civil ways to discuss risk than making statistical straw man arguments too.

Actually, he was replying to a comment that centered on the specific threat level that a particular individual thought he may be facing, so a calculation like this is exactly on point.

Well, that's true. All the same, I think it's a hopelessly facile analysis - the assumption that a bombing is the only possible risk scenario, for example - that's not really responsive to the underlying issue.