Yes, the whole situation is revolting!! I don't eat any dead animal products at all, but would still rank pork the last on the list of meats I would eat under threat of death. Your friend is nuts if he/she thinks they have bred the parasites out of pigs... your thinking is correct, that if they are living in unsanitary conditions and are fed rotting food and other animals' faeces, they will be full of parasites.
I just googled the subject and a zillion links came up. This quote is from the URL below... all the parasites listed are found in humans too, so it's simple equation!
"Internal parasites include various types of internal worms that can naturally infect pigs due to oral ingestion of worm eggs from the pig's environment (pen floors, dirt lots, deep bedding, etc.). Once ingested, internal parasites go through several life-cycle changes as they mature. They compete with the pig for nutrients and may cause tissue damage. Pigs that are heavily infested with internal parasites grow slower and are less resistant to disease and stress. In some cases liver damage due to internal parasite migration can result in condemnation of liver or other organ meats by packing plant meat inspectors.
Large roundworms, also called ascarids, are the most common internal parasite of pigs. Sometimes mature roundworms can be seen in the fresh feces of growing pigs. They appear as long (about 10 to 12 inches), tubular shaped worms that are beige to creamy white in color. Other important types of parasitic worms that can infect pigs include the nodular worm, whipworm, lung worm, stomach worm, threadworm and kidney worm.
Good sanitation and manure removal from pens is an important component of internal parasite control in pigs. Pigs reared on dirt lots, pastures, or in deep bedded systems typically have greater potential for internal parasite infection than pigs housed in confinement on slatted floors. However, confinement housed pigs are by no means immune to infection with internal parasites.
Complete control of internal parasites usually involves treatment with a commercial de-wormer product. There are a variety of products available and almost all products will effectively control roundworms. However, certain products are broader spectrum and control several types of worms including roundworms. The attached table shows various types of de-wormer products approved for pigs, along with example brand names and types of parasitic worms each will control. When choosing a de-wormer, the types of worms controlled, cost and best method of administration for the farm should be considered. The decision to treat project pigs with a de-wormer can be based on the history of internal parasites on the farm and a fecal exam performed by a veterinarian. Pigs exposed to soil or manure from hogs previously infected with internal parasites are likely to have been exposed to internal parasites."