Fun story, when the Gallente and Amarr first met, the Gallente were deeply fascinated by the Amarr and actually were quite fond of their culture. The high seats of the Federation got nervous, believing that if people see a successful civilization besides their own then they would question the necessity of a federation and perhaps try to live as independents. For this reason, the Federation began to demonize the Amarr Empire, largely using the topic of slavery to push this agenda. The propaganda has been rolling ever since.

Source: https://wiki.eveonline.com/en/wiki/Modern_Era_of_the_Gallente_Federation

Quote 1: "The Federation government kept strict control of information regarding the Amarr, fearing that the revelation of the Federation not being the sole and collective representative of human civilization would undermine the entire unionGÇÖs purpose. The highest levels of the Federation slowly became aware of the AmarrGÇÖs practice of slavery, something that would be considered unforgivable by the population."

Quote 2: "To many, the Amarr Empire was perceived to resemble one of their planetside feudal kingdoms from ancient times, that had managed to retain its pre-industrial culture into space and across the stars. Although this oversimplified the complex nuances of a similarly interstellar empire, these Gallente found the Amarr fascinating, despite the disagreements about slavery. The fact that the Amarr were still institutionally religious and conducted themselves in a way that was seen as anachronistic of the spacefaring era was a point that several Federal citizens took to eagerly."