Type 2 diabetes is not a disability Lou, namely because it is entirely reversible. Depending on your experience with it, type 1 diabetes can be life altering, but disabling? Not with today's technology. We live in an amazing world now where insulin pumps and pens mean people can live and manage their conditions very easily and employers, by law, must make reasonable adjustments to accommodate employees with medical conditions unless they want to get in trouble for discrimination. Diabetes is easy to accommodate- just ask for specifically timed breaks to check your sugars and take any insulin, so refusing to take on someone because of something so simple would be an easy case of unfair treatment.
I would say even more so over in America, since suing is so much more common than here in England. Civil lawsuits seem way more commonplace for whatever reason over there than here. Honestly I'm an extremely lucky person to have personal links to someone who can ask for casual legal advice from their work- most people rely on contacting public citizens advice bureaus for support on things like this, which is just that: advice. The idea of taking up actual legal action against a company is extremely intimidating when they as an organisation can afford some nice legal representation whilst you're barely scraping through on £400 a month benefit payments for unemployment.
Most people just move on and find a new job, or maybe go to the media if they feel strongly about how badly they've been treated. Getting slated by local news is a good deterrent for most business