Blood may wash clean, but it never comes off.
There is evil in this world, and if those who can stand against it do not, it will spell the end of existence for good.
But just because they stand against evil, doesn't mean they want to.
Alice would love nothing more than to never have to take the life of another demon; unfortunately, demons will be demons, and demons misbehave.
While it may be true these demons or others like them have said these things to her, all alone in her battlesuit, transfixed by the fresh blood on her own hands, all she can do is ask 'why'?
'Why' indeed...