In essence, he argues that BitTorrent can be a fantastic way of digital preservation, which is the goal of archive.org, and I suspect he uses the word 'pirated' interchangeably with 'torrented', since that's what BitTorrent is commonly associated with.
I think BT makes downloading and sharing accessible enough that more people would be encouraged to download more than they normally would and it is for sure easier for someone to see a request for a reseed for an unpopular torrent and load it up onto their tracker for a few hours than it is to try and rehost it.
As long as archive.org is seeding everything all the bits are there..
It still has a problem with non-popular content being hard to find, but not nearly as much.