Private schools cost money. Somebody has to pay and it isn't the state. If your parents don't want to pay for a private education, then take it up with them. It's fair from Harvard's perspective and the perspective of the general population.
I wasn't aware of the voting that took place to find out what the perspective of the general population thinks. The university I went to was public and the age for being an independent was for federal student aid. Seems like it doesn't matter if something isn't fair.