I think many of you are missing the point, on both sides.
A person or company has the right to refuse to sell their product to people who misuse it. If the Auto manufacturers want to sell their new cars only to dealerships who can service them, that is (and should be) allowed.
The problem is state laws that say the Auto manufacturers can prevent Other manufacturers from selling other products. That is not good and is probably unconstitutional.
It really has nothing to do with the difficulty of maintanance. 8-)