Do you think that I am not bored to death of that myself ? I have been here for more than 6 years now, I have seen my share of the same circular debates. Slavery is only one of them. Religion, Caldari Prime, etc, all have become circular debates. And some like religion often mostly stem out of OOC motivations. Even if I am bored of many of these circular debates, the fact remains that they still are a key, core factor of the lore itself. Denying the debate is like denying that part of the lore, or having an issue with that particular point.
But heh, if we were to ban everything leading to annoying discussions or debates we have seen countless times, you might as well close the Summit. Personally, I have seen them all, nothing new for years. What you are doing right here is to forbid newer players (or just players that find it fun) to have the discussions they want to have, according to your personal tastes. Eventually, even with slaves banned, people still argue about slavery at every occasion, since after all, we do not need a slave to show on screen to start a debate on it. The slaves on screen excuse remains a decoy to my eyes.
And half of the mods being in favor of slavery IC does not lessen the slighest the fact that the rule is anti amarrian, maybe not in essence, but in fact as a result.