While it isn't, unless the chicken is vaccinated (common in the EU, but not done in the US), it is likely to acquire it from its environment. Salmonella isn't just some product of dark infernal factory farms; it's an endemic bird disease and free range chickens are hardly immune (they may actually be _more_ exposed).
Modern farming is more sanitary than any previous time farming. Sanitary conditions are cheaper than having to destroy a thousands/millions of sick animals - you are not allowed to sell sick animals for meat and any disease in a barn will spread fast so modern farmers take bio security seriously.
TB didn't appear with factory farming, nor salmonella. It's about unsanitary farming, period. Poultry scratching through dirt won't be exactly sanitary, no matter how traditional we'd consider it.
You're also putting a lot of trust in the immune system of the animal you're eating. Sure most are fine but you'll eventually get one that is just naturally immunocompromised and when you do, you're in for a bad time no matter what kind of dreamy free-range life it led.
Louis Pasteur began experimenting with heat treating microorganisms in milk in the 1860s; if you have seriously compelling evidence that pasteurization is a conspiracy that spans the globe and has lasted for 160 years, then I'm prepared to be convinced, but otherwise I'm leaning in the direction that the reason that there are microbes in milk is because animals are covered in and filled with microbes
Salmonella is also common amongst wild birds. While some other pathogens are primarily a 'modern farming' problem, salmonella is not; there has never been a time when it's particularly safe to eat raw chicken.
(Actually, modern farming has cut down on salmonella a lot through vaccinating the chickens for it... but not in the US, so this guy is out of luck.)
Salmonella is a hoax now?