First of all, the definition;
the advocacy of women's rights on the ground of the equality of the sexes.
Now, the second part of that definition is dandy, but the term "advocacy" does display a commitment to the movement. In fact, advocacy could lead onto radicalism. Now, the problem is that it only focuses on one gender to achieve equality of the sexes.
I like to equate the logical progression of feminism to that of Marxism. Of course, the more die-hard Marxists may vehemently oppose that mention, and to be fair it has become somewhat of a scapegoat. However, like Marxism, feminism analyses everything among social lines, as something that needs to change. It advocates the "haves" and "have nots", i.e. the bourgeoisie (patriarchy) and the proletariat (working women).
Now, Marxism states that the end stage of the Dialectic principle, after revolution and consolidation, is communism. Communism is pure ideology; an unimaginable utopia for the politically naïve. In order to uphold this naivety against the logical mind, communists can only employ authoritarianism as a form of methodology for their aim. Hence, how in practice, aspiring communist states tend to cause deaths- both intentional and accidental.
How does this relate to feminism? Well, for three reasons;
1) Marxist-inspired states were hypocritical, in that not all working men united, but- as Lenin proposed- a small group of intellectuals to lead a revolution and a government. Likewise, feminism is mainly a movement for white middle class university professors.
2) Marxists tried to change society by force, as opposed to progress through the Marxist stages in history. Feminists wish to overthrow the dynamic of society by force.
3) Whilst authoritarian feminists and Stalin fanboys are in the minority in their respective movements, they do still exist within their movements. Their opinions are eerily similar to the original ideology.
Does feminism logically conclude to authoritarianism? I don't know, but if a truly feminist state was to occur, it would be restrictive on the freedoms of even its target market.