If the two hurricanes and two tsunamis that rose to the level of 'astonishing' during the past decade are the only time that people grasp their likelihood, it is counter productive to treat these events as irrelevant. The same goes for DDoS attacks.
It doesn't matter what people think about this specific issue, since there should be no doubt that there will be many more attempts at this type of vigilantism. No one wants their company beholden to other people's whims and angers, so they should have better defenses. Whether competitors point out their failings or not should be the least of anyone's worries. The capacity to handle attacks up to varying levels of size shouldn't be an impolite or unmentionable subject, it should be a key part of business contingency plans for businesses and their customers.
FWIW, I never claimed that, and I don't think the OP did either. At least for myself, I am very specifically referring to the "black swan event" situation, where something external, unlikely and damaging happens to a competitor. In that case, I don't see how showing some restraint, and not launching a targeted campaign to try and leech their customers, is anti-competitive. And to the extent that you can, somehow, define it so, I would argue that any damage is so absurdly trivial that it can be ignored.