It's a perfectly valid word. As for Ducane, I was just going with what Voyager showed about the policies of the Temporal Integrity Commission. In "Future's End," they were willing to destroy an entire starship based on an unproven suspicion that it was the cause of a disaster -- not even bothering to investigate first, just charging in guns blazing. And in "Relativity," Ducane arrested the "present" version of Braxton for the crimes of his future self -- punishing a completely innocent man for something he not only hadn't conceived of doing yet, but would be prevented from ever doing at all. That's horrifically unethical, a profound violation of the most fundamental principles of justice. Those told me that the Federation of the TIC's era had lost track of its core values and become a more oppressive state.
Besides, Ducane was just kind of smarmy. There was something shifty and mean about him, and in the context of the above, it made sense to play that up.
Even aside from all that, I think it was a good idea just for variety's sake. It wouldn't have been as interesting if all the uptime agents were nice people with compatible agendas. It was more fun to have the agents from different eras constantly bickering and clashing. And it was worth touching on the idea that societies sometimes lose touch with their ideals and go through dark periods. We can't assume the Federation will remain benevolent forever.