A torrent containing a link to a file that is illegal to copy has no legitimate non lawbreaking use case. There is no legal way to use a torrent of Portal. I notice you mentioned in a separate comment that some items, like grenades, can only be used in illegal ways. This is true also of torrents that the Pirate Bay hosts.
Yes, it is true that legal torrents exist; however, the Pirate Bay distinguishes itself as having both legal and illegal torrents. That's what the difference is.