Clem beat me to it. There is zero reason to protect this deer. It's a genetic deformity. It could have been passed down as a rare recessive gene from the parents or it could be a genetic mutation. Either way, there's a chance that it could get passed on to more offspring. It is also possible that a doe like this could have completely normal fawns. There is also the chance that she has nothing but discolored fawns that never survive because they lack the natural camouflage that they were intended to have.

Fred is right too. You can't impact the herd genetics by killing this one deer. But if it was caused by a mutation, you could keep it from spreading in this scenario. There is evidence of white deer being protected leading to a greater abundance of them.