@The:
Be Sanji or be a "do not care for anything" swordsman, pick your choice man.
Why should he choose between two extremes?
Seeing things just as "black and white" is exactly what younger people do. Why can't he be in the middle(depending on the situation etc.) like most real-life people are?
I'm pretty sure there are not many real-world Sanji's around. Neither there are many people who completely disregard gender (except maybe in some cultures).