There seems to be this idea that started long ago – that Sanji is a womanizer, to the extent that even the creator, Eiichiro Oda agrees and has referred to him as such. Now, you might think the creator’s words are gospel to their works, but not when it comes to a fundamental misunderstanding of the meaning of a word, here, in contrast with the character’s contrary attitude, behavior, and actions.
Womanizer; (noun, derogatory) “a man who engages in numerous casual sexual affairs with women.” Sanji has never engaged in ANY sexual affairs with women, so that definition is completely incompatible with his character.
Womanizer; (noun) “a man who likes many women and has short sexual relationships with them.” Okay, there is actually some truth to this version of the term, so as far as Sanji liking many women, but there hasn’t been any suggestion of Sanji being sexually intimate (beyond arousal) with any, never mind many women in either the anime or manga, so this doesn’t work either.
Where it falls flat, can simply be shown through comparing him to any character that actually IS a womanizer (here, I’ll be using an example outside of anime, since it’s an easier comparison to make), e.g. Barney Stinson is a womanizer; he chases women, sees conquering them as a goal/challenge (i.e. he’s been keeping track of how many he’s slept with and even made challenges out of how many he could sleep with in a given time-frame, i.e. a day/month), and he IS “a man who likes many women and has short sexual relationships with them” & “a man who engages in numerous casual sexual affairs with women.”
The key difference between the two being how they treat women. Barney treats women with very little respect, and acts charming (and uses various other personas) to deceive women into sleeping with him; he sees them as objects of his desires, to pursue and conquer, and then discard and move onto the next.
Whereas, Sanji genuinely cares for and has the utmost respect for women to the point where he places virtually every attractive woman he’s ever met (and will meet) on a pedestal above him; and he resents anyone who dares harm a lady, both physically and emotionally. He’ll fight for a crying woman he just met, because to him it is an unforgivable act to make a woman cry.
Sanji has adopted a code that restricts him from fighting women. Whether you think that’s sexist or not isn’t the debate here, so please don’t open up that can of worms. He loves women and falls head-over-heels for anyone even remotely attractive he comes by. He’s willingly made himself subservient to essentially any and all attractive women, to the extent where he’d jeopardize his life to protect one he just met. To Sanji, women are more precious than his own life.
Basically, every form of the term “womanizer” and its synonyms (e.g. philanderer) at most capture only part of Sanji’s tendencies (in so far as him being infatuated by, and “chasing after” women), but without the key defining features of being one (actually having any romantic or sexual relationships with them). He can barely contain himself around (attractive) women – from the ever-so-popular nosebleed response, to the expressive hearts-for-eyes reaction, to going out of his way to satisfy and impress any woman he meets in any way he can (and even then, he will try beyond what he is capable of doing just to make a woman happy).
Sanji is a cool guy. He’s a kick-ass chef with strong ambitions, who smokes, and has a traumatic past that inspired him to have a greater appreciation for food (hence, tied-to being an amazing chef). He’s an interesting character, both cool (when he’s serious) and funny (when he’s making snarky comments, or acting silly around women), and smooth as fuck (when he’s complimenting women or cooking). Also, he’s incredibly kind (something womanizer’s tend to either not be, or pretend to be to get with women and move on), and has unbreakable moral values (would rather die than fight a woman).
He’s expressive and passionate, histrionic and intense, and he doesn’t care if he makes a fool of himself, especially if it can make a woman smile. He’s compassionate and generous too, which is tied-to his love for cooking for others and seeing the satisfaction from eating his food.
Sanji is, and has always been a gentleman. A perverted one? Sure. But a gentleman nonetheless.