The thing with Nami and Vivi is that they don't get in the way of Zoro/Sanji. :/ I mean, Sanji is, well, pretty hetero for Nami and Vivi, but he's like that with all women. And it's made pretty clear that neither of them like him back 'that' way. In fact, it's arguable that those girls are more gay for each other than anything else.

I don't have a problem with Zoro/Sanji, as long as people keep it IC, which is terribly hard to do.

So yeah. I think this person the secret is referring to might just hate them because there are OMG GIRLS in the show. Ugh. :(