That is the user's choice. If a user comes to a bookshop wherein they are allowed to read the books for free but only in the store, they have little right to argue that they should be allowed to take the books home like paying customers because the store's lighting is not to their liking and they want to read in 6000K. They are free to picket outside and claim that the store is ruining people's eyesight, but no one sane will take them seriously.

Furthermore, the appropriate solution to this "problem" would be to stop letting people read anything for free.