Why are people acting like Sanji hit on a child? Is there a panel where Sanji flirted with Bonney?
Only thing I can think of as bad is the "Lady Radar" comment, but, that's not really Sanji being romantic, Sanji's just... Sanji.
I highly doubt Oda will actually have Sanji sexualize Bonney if she is a child. Oda's the one drawing Bonney's ass, not Sanji, he's just trying to save her life.