[TheChaplain]

You are free to do whatever, but companies are also free to choose who they conduct business with.

In the case of Ferrari, their products are essentially also rolling advertisements, so modifying them goes against what they are trying to sell.

[danbruc]

That line is not that clear. Putting up a sign in your shop selling only to white people or not selling to Jews will get you in trouble in quite a few jurisdictions. On the other end of the spectrum you have things like a bouncer rejecting people at the door because they do not fit in. Also the difference between not allowing to paint your Ferrari blue and not allowing or making it hard to have your John Deere tractor serviced by yourself or a third party is not that obvious.

[TheChaplain]

I am 100% certain, that if you go to a Ferrari dealer and buy one of their cars, they will clearly inform you of their rules.

Of course you can have a friend to buy it for you, but again, it's Ferraris choice who they want to conduct business with as long as they follow the laws to the letter. Their car is their brand and they want to protect it.