He's using a well worn legal tactic that has been used in the UK and other parts of Europe for several years now. It's a form of extortion.
Google " Davenport Lyons " and " ACS: Law " {same people, they set up a new company to do piracy cases} to see what they are doing. I think DL getting banned from practicing law in several EU countries for dirty tactics is why they started ASC: Law.
Their "proof" is extremely weak and they have sent letters threatening to sue to printers, dead people and countless variety of other non sense.
They don't take people to court, despite their claim to have successfully won a case and awarded £16,000, they rely on your fear of court to get people to pay. No one can find any evidence of the supposed case where they won the $16,000.