Basically it was Skynet’s fault. Which would be a satisfactory excuse if Skynet actually existed, which it doesn’t. People wrote the software, people deployed it, people were careless enough to not pay attention to its output, and people stood to profit from it. The background is interesting, but does not absolve the concerned parties of responsibility.
UPDATE: This tweet sums it up:
While some people are being extremely patronising and superior about auto-generated t-shirt slogans, the rest of us think ‘keyword filter’.