I think you might be accidentally trailing off the topic. The topic is why are Atheists viewed so negatively and one of my reasons was that they can't be trusted as well as most spiritual people because they have no moral authority.
It COULD run in a way we can differentiate if more Atheists thought about the concept of subjective morality. Only a very select few have fully thought out what morality means in atheism, which is nothing. You follow your own subjective morals but don't know why. You can say that you wouldn't steal anything (even if you knew you could get away with it), cheat on a spouse (even if you knew you could get away with it), kill your worst enemy (even if you knew you could get away with it), but when it boils right down to it, there is no real reason why you follow these morals because there is no moral authority (if there were no God), the only person saying that these things are without a doubt bad is you. You have no reason to believe in morals because without a God, morality, right and wrong, are just made up concepts like a flying spaghetti monster.
Am I saying throw morality out of the window now? No, because I do fully believe in God and fully believe in objective right and wrong.
I understand your point to the topic question and agree, as for my question:
Rules people create for themselves (beyond shortsighted cost/reward analysis) depends on the identity (their hearts Romans:2-14-15) they choose for themselves. That 'nothing' is actually a changing environment and individuals responses to it. Yes, in their mind, they are made up concepts, not necessarily individually made up, but from forces of the community and parental influence as well.
The presence of the bible is like an achor to peoples perceptions of morality (if they accept it), consistency feels safe and stop internal subjective moral thought's (as described by Romans 2:14-15) from a prolonging accusation of what is right and wrong, because the answer an anchored person uses is more clear. Imagine the horror of thinking the environment could make your morality change in such a way the current morals are thrown out the window... that's where I think the fear comes in. However, an adults mind is more fixed in it's early lessons, it is the morality of the child that is much more influence-able as to warrant fear.
As an argument for the existance of objective morality, i.e. which is true?, the achor has to be proven to be objective (i.e. prove God), or some elements of everyones morality are to be proven unconditional (but does necessarily prove God). Since the former is the premis in dispute, using morality to argue backwards for God doesn't work as a truth based argument...BUT, as you say, there are natural consequences of an atheists premis and a christians premis (i.e. What morality is!) that should be accepted. Hard for angsty teens to accept, when they've just been through a 'right and wrong' lesson