Sexism, much like racism, is often not based on intentional hostility or malevolence, (even though it causes pain and has victims).   It's a blindness to knowing that what one assumes is 'normal' status, is in fact a privileged status.   

As a boy I knew my life would include work, possible military, sole income earner, likely to go to college, head of my eventual family, king of my castle.  I could play any sport that I wanted, take any class I could qualify for, do any job I desired(and do it better than women).  I was 8!

That privilege was very real in term of social power.  It was very wrong in terms of women's abilities and deserved respect.   The changes in gender expectations grind against the past learned values of children.     These learned values of male superiority, including those wrapped in religious language and supported by parental teaching, will take many generations to change and will never change for some.