I think the reason that the humans became the good guys really was because of how humbled they'd been after a generation or two under the Alliance's control. They KNEW what horrible things they'd done to these species.
And, if we're getting really picky, it's really just O'Brien who we can qualify as a 'good' human. O'Brien and Bashir are the only one of our main characters who we see in significant roles. The other characters might be willing to shoot first and then shoot anyone who asks questions, but we don't actually see them in major roles.
And, really, we only see snippets of these characters anyway, always against the aggressor Alliance forces. We don't know what they do when they aren't fighting the Alliance. Are they strip-mining Bajor? Mass producing other ship designs they stole from DS9's database to utterly wipe out the Klingon/Cardassian species? Torturing prisoners? (...Okay, so we KNOW Bashir is, but we've already seen he's PSYCHO anyway...)