While the Federation Council may be a democratic body I would imagine that not all of the member planets are what we would call democracies. Ardana in The Cloud Minders was a Federation member but the Troglytes certanly were not casting votes either on their planet or in the Federation Council. In Amok Time T'Pau asks T'Pring if she is willing to become the property of the victor. Perhaps married Vulcan women don't vote either, letting their husband deal with such matters. The Federation would be pretty boring if all the planets looked like mid 20th century American their politics.
And it would be morally disgusting if it did not protect the inalienable right of all of its people to participate in the democratic process and to be equal citizens before the law.
That sounds like the arguments people are using against same sex marriage. It's not the way our ancestors did things. It was good enough for them. It's good enough for us and we say it's good enough for you too.
Aliens are not us. We are not them.
We do NOT impose democracy on
others. We do believe that every
planet has a sovereign claim to
"Human rights." Even the name is
racist. The Federation is
basically a "homo sapiens" only
So the Federation does not demand that every culture be democratic but they still haven't gotten to the point of realizing that every culture will have it's own idea of what constitutes a right.