Oboro Tennosuke, I really think that Ace is a legitimately good person because of his actions in Alabasta.
He didn't have to help out the fake rebel army leaders by building their character and getting them to be brave people rather than cowards, and he did it because he knew that despite what they were doing, they weren't bad people.
He had no reason to do that at all, he could have just come out of the town and been like, "let's be on our way, Luffy!" and they would have left. Instead he and the Straw Hats orchestrated that little scuffle.
This adventure does not take place in the manga, and because it doesn't it is proabably a bad idea to use it as evidence.
Oboro, I will send you some soup in the mail. However, I do not think that Ace is a bad person.