It absolutely is so black and white. If I buy a computer from you and you send me a parcel which explodes in my hands, no amount of hand-waving is going to get

It absolutely is so black and white. If I buy a computer from you and you send me a parcel which explodes in my hands, no amount of hand-waving is going to get you out of this -- this even holds if you just distributed notes "Call this number to get your own personal computer free of charge!". And just as a computer reseller/free-computers-for-everyone-distributor has an obligation not to send bombs to people who asked for computers, a website owner has an obligation not to serve malware to people who asked for content.