That's a good point, but we don't only sell blunt knives in case someone goes on a stabbing rampage.

Nobody would blame the knife for the rampage.

Ironically, a large portion of people are willing to support legislation like the Brady bill which would make it legal to go after the manufacturer of guns which are used in mass shootings.

Many people in america do blame colt, Winchester, Remington, etc for ever even manufacturing these weapons in the first place. I've heard that the UK is also very strict about knives so maybe some of that can happen there too...