It is very fair. Who would want their original machines to be modified. We don't have to modify the John Deere machines. They are valuable and hence should be maintained to make them rein. John Deere cites the possibility that circumventing technological protection measures (TPMs) for gaining access to ECUs could cause software systems to malfunction and create a public safety risk, noting that an agricultural vehicle can weigh over 44,000 pounds
Yes, it's fair the John Deere makes it impossible to alter the software installed in their machines. Sure, it would be nice to change things up to fine-tune the machines' function. But the problem is that when people try to modify lawn mowers and other machines, John Deere could be held liable and sued if something goes wrong. So making their software off limits actually protects their customers and the company.
Yes, it is fair that John Deere makes it impossible to alter the software installed in their machines. This company has the right under current law to install whatever software it sees fit in its machines. If lawmakers feel that this poses an unfair advantage, they can attempt to enact laws prohibiting this practice.
When you make it impossible to alter the software of an invention, you impede progress. As you introduce things into the world, you have a responsibility to mankind, for your invention was not purely your own. You learned from others and you modified other inventions. Now you have the responsibility to pass your knowledge and inventions forward for the betterment of mankind.