Peaceful and innocent in contrast to space humans, who are waging genocidal war against aliens and having much higher mortality rates and less fluffy conflicts in general.
According to dialogue in EP3, Gargantians don't kill pirates, but rather negotiate with them and that holding people at gunpoint such as when the pirates boarded the ship is just for show and part of negotiation. In the scene shown in the picture Bellows says that the game's changed now that blood's been spilled, implying that they hadn't killed pirates attacking them in the past. Later the Commodore states that the pirates are coming for revenge and won't back down until blood's been spilled for compensation, and when the pirate queen attempts to kill the Commodore it's implied that killing the Commodore would settle the blood feud for the time being in some sort of weird equivalent exchange. So they've got some kind of truce with the pirates where they poke in to pillage every now and then, but no one gets killed out of mutual respect for human life (?!) and big murderous attacks are only done in response to grave derision.
There's some weird stuff going on in the setting that needs to be explained for the show to make sense, but the show hasn't done any satisfactory exposition on how the relationship between colonists and pirates works in the setting, why there's supposedly universal respect for human life on all sides, why the pirate assault in EP2 did not warrant Ledo killing the pirates (perhaps raping a bunch of sluts who don't mind and taking a small amount of stuff before being chased off by the defense patrols would've been all that happened or something?) and other things.
tl;dr: The show's a bit retarded and you should watch EP3 to see what I'm talking about.
Also, the two girls in the picture you're talking about are the pirate queen's two top goons or something, and the chains are indeed just a pirate fashion statement by the looks of it. They're displayed having a great old time and there's nothing suggesting slavery or imprisonment or anything like that.