Shouldn't the fact that the negotiator was representing the Cardassian government show that she was a participant in a democratic republic? It is kind of a given. Akaar didn't say, "The Cardassians have a democratically elected government now." The statement seemed to be about the negotiator specifically. Besides the political leadings she has, she is still a Cardassian and they are new to this form of representative government. Her actions in the negotiations seemed more representative of a "Cardassian" than a "Democrat." Pointing out that she is a democrat seems partly irrellevant and partly judgemental of other political persuasions.
Plus, as I said, Romulans are democrats and Klingons are militant. So does one form of government really incline a people to be friendlier with the UFP? They may be democratic, but they are still Cardassians. A culture doesn't change in a few years time.
To quote Ezri- "Am I overreacting!?!"