Interesting point of view Robby. While your facts are indisputable, I can't agree with your analysis.
@RobbyBevard:
This chapter, our new eel friend is talking about how the arlong pirates were destroyed, but also about Hachi, and Luffy striking the Tenryubiito, so he knows all about both.
But you notice that he did not mention Luffy's freeing of Jimbei, the leader of FI as of two years ago, as one of Luffy's positive acts. This implies that Jimbei has fallen out of favor for those guarding Fishman Island.
Also, Hammond is wearing the tattoo of an Arlong Pirate despite having a stronger looking crew at his disposal than Arlong ever did. This gives us two possibilities:
1. Arlong has broken free, gotten a power up, and is the leader of the "New Fishmen Pirates" to which Hammond belongs, and possibly runs all of FI.
2. Arlong was sentenced and executed by the WG, making him a martyr figure for the fishman power movement.
Option two seems increasingly more likely because if Arlong were running things, Hammond would have to check with him before forcing Luffy, Arlong's former enemy, to become his nakama. Also, Hammond credits Hacchi for being a former nakama of Arlong, not a current one. Hacchi's redemption arc means that he would reject Arlong today, and therefore if Arlong were present, Hacchi would lose his esteem with the New Fishmen, and therefore saving him would lost its relevance.
Arlong is one the few pure racists iredeemable evil asses of the series. The guy committed one of the few on screen blatant murders. OP, as good as it is, is still a shonen and isn't going to spend time trying to redeem or make us sympathetic to a character like that. (Its enough that we know he once wanted to ride a ferris wheel.) Especially when we had the entire Impel Down arc redeeming villains left and right.
I think you are completely missing the point that Oda has introduced with this racial war between the fishmen and humans. Arlong was a murderous bastard that was fighting for the rights of an oppressed minority. That makes him a hero to that minority. He's a former slave that had no compulsion against killing the people who he felt subjugated his entire race. Is that irredeemable? He was trying to establish a new Fishman homeland in East Blue, a place where Fishmen could walk freely without being enslaved(shabondy), forced into ghettos (W7, and likely the rest of the world,) or subjugated by the WG and at the whim of every passing pirate (FI.) In order to do that, he'd have to have complete military superiority over the Marines, which required Nami's maps.
So, he was willing to resort to slavery(of nami) to accomplish that goal, but from the point of view of a repressed Fishman, even that would be justified as "for the greater good." Is that evil? Were the Haitians who murdered the children of the white plantation owners who tortured them daily, "irredeemably evil" or somewhat justified in their outrage, if not their actions? Oda has set up a realistic situation of two peoples on the brink of a genocidal war here. Saying which group is irredeemably evil misses the point.