@Xai:
I think he wants to say that Jimbei considered former slaves (like Arlong) to be inferior, but was forced to treat former slaves as equals by Fisher. This annoyed Jimbei, and he murdered Fisher. Or something like that.
At this point, anything goes. No one else but the Sunny Pirates would know who was a slave at the point they were hiding their mark. One could easily use, that piece of information, against another. We mustn't forget "Jinbei unleashed some monsters on the East Blue" was said in the Arlong arc. Who knows… Maybe Arlong was forced into it, if he was discovered to be a slave he would have lost a lot of respect.
The Sun symbol simply hides the woe of those affected amongst those unaffected, but the woe still remains and the "Less then Human" fear that follows.