1. Depends on the girl. Its human nture to sexualize everything. You don't even need a drawing, even a kinky story with no image at all can get the blood flowing. The real problem for me starts with: Robin and Nami are great characters. Nami herself, though beautiful, is very sweet and inocent, kind hearted. It's not OK for me to see or imagine them in gruesome sex positions some r34 out there create. There are even Momo r34 with the SH girls. That shit is wrong.
Also, 100% prefering 2D over 3D is not healthy either. If a regular dude still go out for girls, try and have normal relationships for still see the occasional doujinshi of random young women that are not stablished characters in any serialization, I don't have an issue with that. But, as I said, perveting the OP characters, FALLING IN LOVE with 2D girls, etc, that's not good.
That's my personal opinion though, anyone can go do whatever the fuck they want.
2. Man, that's actually a very good point. PIRATES is a really strange choice of theme really. With Haki, the fruits and everything, Oda could go for anything he wanted and we would still love it. He could even go with Ninjas since OP is older than Naruto and we would still love it. But he went with PIRATES, and me, as a paying costumer who buy offical signatues and offcial products whenever I can, have the right ro criticize what I think is wrong. If you want to be the king of PIRATES, you must be a good PIRATE. Luffy is terrible as a pirate and so is his crew. Does making friends and reaching a final island makes a boy king of anything?
Roger became the King of Pirates by being the badest man in the ocean. If you pissed him off he would murder you and everyone you loved, take Squard for example. Roger took shit from nobody. He made whatever alliances he could to win, even teamed up with the Marines to destroy his greatest rival pirate. He was the strongest, has a lot of street smarts and nobody would dare to cross that mfer. THAT is a PIRATE KING.
This new concept of good virgin pirates that save everybody is a bit odd. Hope Blackbeard beast the shit out of Luffy.