Hate to sound pretentious but I feel like concluding that a writer hates one of their main characters after evaluating their work is a bit of a disservice. I mean, Oda spent time writing Sanji and giving him screen-time, regardless of the end-result and anyone's dissatisfaction.
Of course not everyone will be happy with it but that doesn't mean Oda hates the character. Instead of criticising his work, it's basically pretending whatever issue you have with the character was on purpose solely to spite the character which doesn't make much sense to me. Oda isn't perfect but concluding the only way a certain character has issues is because the writer dislikes them seems strange to me. The character just doesn't appeal to you, that's all.
I just can't see Oda outright hating Sanji. Why give Sanji so much focus if you hate him? Why have Luffy tell Sanji he can't become the Pirate King without Sanji if he disposes the guy? Why give Sanji more screen-time than pretty much all other characters in this manga, save for Luffy, Zoro and Nami? Why have Sanji prove himself as one of the greatest in his field by doing precisely what guys like Bege didn't think he could by satisfying Big Mom? Why continue to give the guy clashes and have Luffy tell Neku that Sanji's important for the alliance by highlighting him as worth 1000 men? It's not that Oda doesn't like Sanji, it's that certain people don't like him and that's fine but I disagree strongly that Oda hates Sanji.
This goes for most characters. Oda is just trying to appeal to readers with most characters. Doesn't mean he hates certain characters because you don't like them. That's assuming he has the same tastes and preferences as you when it comes to his characters. Unless this is just trolling then ignore this post.