As for reasons stated by Fireplay, Algalon, silmmaril, and cptenn94, gotta say I disagree. Plus the premise of your thread is a little off. Characters like Smoker, Aokiji, Coby, Garp, Tashigi, etc have been shown to be genuine good people, who have a different sense of justice than people like Akainu and others. Oda shows that not all people affiliated with the WG is bad, but people who have more powers than others have a warped sense of what is right and wrong. They take things too far sometimes and it can be perceived as evil.
We are shown that in the manga, evil does not lie within a group but within individuals. Not all pirates are evil, but some of them do some devastating shit. Not all of the WG is good, we've seen them act as heroes before. IMO, the moral side of One Piece is not only developing still, but Oda is trying to show that generalizations are not the way to go when it comes to a side of what group has the right or wrong morals.
We are shown that in the manga, evil does not lie within a group but within individuals. Not all pirates are evil, but some of them do some devastating shit. Not all of the WG is good, we've seen them act as heroes before. IMO, the moral side of One Piece is not only developing still, but Oda is trying to show that generalizations are not the way to go when it comes to a side of what group has the right or wrong morals.