Star Trek: Deep Space Nine, Season 2

Quark:
I think I figured out why humans don't like Ferengi.

Benjamin Sisko:
Not now, Quark.

Quark:
The way I see it, humans used to be a lot like Ferengi: greedy, acquisitive, interested only in profit. We're a constant reminder of a part of your past you'd like to forget.

Benjamin Sisko:
Quark, we don't have time for this.

Quark:
You're overlooking something. Humans used to be a lot worse than Ferengi: slavery, concentration camps, interstellar war. We have nothing in our past that approaches that kind of barbarism. You see? We're nothing like you: we're better.