I too am unsure of why various states ever decided it was a good thing to protect albino deer. The white coat as well as differences in pigmentation of their eyes and other aspects of their physiology would seem to make them easy prey, and I suspect that most succumb while quite young.
HOWEVER... if they are so inferior how is it that some live through their first year and beyond? Might it be that some albino deer are unusually cunning, or have other qualities that allow them to avoid normal predation? This is not to say that the gene for albinism is connected to any factors that enhance the survivability of certain albino deer, but merely to say that if one can survive to 1.5, 2.5, or 3.5 years despite being albino, then perhaps they have some other genetic qualities that are valuable.
Besides, given the nature of the genetics of albinism, most of them result from the mating of a buck and a doe with normal coats, and killing all the albinos would do little to reduce the number of them in a population.