Did you find that The Federation walked the line between democracy ,and fascism more in DS9 then in previous Treks?
Hardly. Even at its worst in DS9, the Federation was still firmly in the realm of liberal democracy. There's no evidence whatsoever of the basic traits of what we call
fascism
You hear people using the term socialism (and fascism) a lot, usual as a metaphor for "more government than we already have." outside of the novels the Federation government is largely unknown. But let's see:
Fascists claim that pluralism is a dysfunctional aspect of society -- Centralization of power in the federal government.
Debatable. The Federation seems to be just that -- a federation. We know that Federation Member States have a lot of power over their own affairs -- ritual murder is legal on Vulcan, for instance. And we know that Federation Member States maintain diplomatic missions to one-another, separately from the Federation itself, from ST09, wherein we discover that Sarek was revealed to be Vulcan Ambassador to Earth. We know from "Journey to Babel" that when the Federation was on the verge of a civil war, it convened a conference of ambassadors from its Member States to decide on the issue of Coridan's admission, and that the various Member States had some very different economic interests in Coridan's admission. All of which seems to imply to me that Federation Members have strong powers and that not all power is centralized in the Federation government -- it seems to be a genuine federalism.
Fascists believe in collective identity -- Kirk often spoke of the Enterprise was a Earth ship and of Earth science, Earth colonies.
No, Kirk only spoke of the
Enterprise as being an Earth ship in the early episodes, before the writers had invented the Federation. Thereafter, he and all other characters in TOS, TNG, DS9, and VOY referred to their ships as Federation ships.
Fascists oppose and blame capitalism -- Picard, enough said.
Fascists also oppose socialism and communism. That one is opposed to capitalism does not make one a fascist.
no suppression of free and fair elections -- When have the characters on any of the shows spoken of elections to the Federation council.
The mechanism for elevation to the Council is canonically unestablished.
We know from DS9 that Bajor was a democracy and that, when it was about to become a Federation Member, Federation Councillors would have to be "selected" -- implying either an election or an appointment by the democratically-elected government of Bajor. This would be similar to how the United States Senate used to be determined; state legislatures would elect their state's Senators rather than have a popular election.
The novels have established that every Federation Member State gets to determine for itself how its Councillors will be selected -- Betazed does direct popular elections, for instance, while the Bajoran First Minister appoints their Councillor with the advise and consent of the Chamber of Ministers, and the Andorian Councillor is determined as part of the Andorian Cabinet on the basis of which Andorian political party wins a majority of seats in the Parliament Andoria. There is no evidence of any Federation Member States that are not themselves some form of democracy.
no evidence of a single-party state -- Evidence by omission I suppose, certainly the member planets wouldn't seem to be sovereign state/entities.
A non-sequitor. I'm referring to political parties, not to the division of power between the central and local governments.
Can a group of planets form a political bloc and oppose the council?
That's a bit like responding to someone asking if multiple political parties exist in the U.S. by asking, "Can a group of states form a political bloc and oppose Congress?" It's an entirely separate issue from whether or not multiple political parties participate in democratic elections.
For the record, the novels have established that Federation Member States have the right to secede from the Federation, and that worlds such as Cait have exercised that option. They've also established that there are no Federation-wide political parties, but that every Federation Member State has its own political parties and that Federation Councillors can and do often form issue-by-issue political alliances with one-another.
no evidence of a dictatorship -- If the Federation is ruled by a small central group of non-elected powerful elite, that would be a dictatorship.
Again, it has been canonically established that the Federation President is democratically elected; that alone keeps it from being a dictatorship. As I noted above, the canon has not established how the Council is selected, but has implied a democratic or semi-democratic mechanism.