Jim, the reason you do not see any reasons given for "we need to define atheism without defining the scope as well", is that nobody has even suggested that.  You know what else you don't see any reasons given for?  You don't see any reasons given for using giraffes instead of horses to pull carriages.  Nor do you see any reasons given for wearing shoes on your hands instead of your feet.  I assume you're not doing this intentionally but you're making what's called a straw-man argument and it's not the first time you've done it.  Please be more careful as logical fallacies, whether deliberate or accidental, in addition to irritating others, tend to impede/obstruct progress, and i assume in good faith that neither one of these is your goal. talk