It was really not good enough for Amazon to "explain" that its misogynistic T-shirts were generated by a computer algorithm without its knowledge. Companies, however big and fashionable, have to take responsibility for what they sell – as they do for their tax decisions. That's all part of the brand – in Amazon's case, one which is now doubly damaged.
That said, the wartime slogan that seemed so admirable and apposite when it was revived after the 7/7 London bombings – and which then gained a new lease of life in "austerity Britain" – had long lost its allure. The variations on the theme were becoming tiresome. There are only so many activities that can plausibly, or humorously, follow the injunction to "keep calm". A slogan, like history, could be said to repeat itself first as tragedy, then as farce. The next and final stage is debasement, from where there is no return.