It wasn't just the spam email - if you go back to the Mail report (which I quoted on page 1 of this thread), it says:
"Joyce, who has a string of convictions, admitted searching for child abuse images on the internet while he was having problems with alcohol. Ipswich Crown Court heard that he claimed the vile footage arrived on his computer in a spam email – but confirmed he was aware of it."
So it's not just that he unluckily clicked on a piece of spam email - he actively went looking for this stuff. Vile POS.