Seriously, some people here legit start foaming at the mouth whenever someone says something good about Sanji. What is it about Sanji that makes certain fanboys hate him so much?
I don't hate Sanji; I enjoy his character, but I think the hate is a combination of things.
People seem to primarily hate him because of his
perversion and inability to strike women (
Chivalry).
Sanji is Oda's go-to character whenever we see any scantly clad woman or just new "attractive" women in general, so that gag gets done a lot. I think we're also at the point where many people are just sick of stuff like that. However, It's not as bad as FI, for example.
As far as the Chivalry is concerned, people always go back to him not hitting Kalifa during Enies Lobby, despite Robin being in danger. I can see why people would hate this because it
is absurd in that scenario. However, I'm also OK with it since that's what he was raised to believe from early childhood, so it is what it is.
You also have people who feel a character's combat "feats" determine their worth, and since Sanji hasn't "won" any fights, this plays a part in their perception of him.