A question of purpose, in regards evolution ...?

Evolution offers a person the "freedom" to set them self up as the final arbiter of what constitutes "right" and "wrong". If evolution is true then there is no higher being to whom a person must give an account of how they lived their life when they depart from this earth. Instead a person can just do what they want as long as they can get away with it in this life and tell other people that morality is subjective and so they shouldn't be subject to criticism since what one person perceives as being immoral or moral is only their personal opinion and there is no universal standard by which to compare various viewpoints.