If we follow the readings of Marx we can only conclude that a revolution is a completely authoritative and violent act upon which we dispossess a group of people, in this case a class, the bourgeoisie, from their means of production, they will not let it go peacefully. Keeping things this way requires what Marx called the dictatorship of the proletariat, which in itself is also an authoritative act. Marxism is inherently authoritarian, but not because of the reasons you believe, because achieving a change in the relations of the means of production always ends up in violence. The same happened with bourgeois revolutions against feudalism. The liberal or whatever thing you are okay with, as long as class society is maintained, and a system that handles the means of production is sustained, it will be authoritarian, because it imposes the will upon the people. That's the basic difference with anarchism, we believe in the same, buy they think that once they do a revolution, they force they will use to maintain it will not be authoritative. We own that.