There is some confusion here. Are you saying that Social Libertarianism is separate from Libertarian socialism? The latter is non-hierarchical, as is anarchism. My understanding has always been that it loosely encompasses most/all forms of anarchism.
Sorry for the confusion; I got my terms mixed up, I edited the thread title to reflect this.
the only way to get rid of "hierarchies" is to force people to not form "hierarchies"
Incorrect; there are always at least two ways to solve a social problem. The first is through force, as you mention. The second is to naturally remove the incentive to partake in the problem, which is what you'll have to get used to if it's a voluntaryist society you seek. This is true for all social problems; we can force people to not have abortions, or we can construct a society in which you'd actually have the time, money and energy to raise a child; though abortions would never truly go away, it might then be crazy to think of denying a person to live in such a world, as opposed to the right now, where most people who abort have none of the requirements I mentioned above.
In the case of hierarchies, the alternative would be for there to be no reason for people to want to form hierarchies; although it is in my belief that simple hierarchies can be good, massive hierarchies where just a few people employ several thousand other people and rake in massive amounts of profits, is not necessarily a good thing, as this leads to a concentration of power. What state socialists often forget is that, though they want to spread the wealth around, they like to do this with the bigger concentration of power, which leads to the wealth getting sucked into the black hole of government and their efforts are all for nothing.
If hierarchies are beneficial to society, we must look at government and ask ourselves if this is true. But again, as hawkeye stated, hierarchies can also be voluntary; because I've never lived in a voluntary society, I cannot make a real verdict as to whether hierarchies are ultimately good or bad. As herzmaster pointed out, the point is that massive hierarchies cease to be possible, meaning capitalism as we know it today (corporatism/cronyism) would no longer be possible.
Because people rather put someone in charge who knows wtf he's doing, rather than your stinking lazy hippy ass.
And in the scenario where everyone knows what they're doing?