I keep reading versions of this (I paraphrase): "if the state disappears tomorrow, a bunch of gangs will compete to fill the vacuum and we'll end up where we started."
This is true whether you believe that human biology has us rigged to hurt each other at fairly constant rates wherever and whenever (violence is hard-wired) or if you believe that good parenting results in relatively less violent adults and offers hope, however slight, for long-term improvement in the human condition. Either way, current humans are violent and the sudden disappearance of what we call states would not dramatically change the human condition.
In the meantime, it's worth making the case against state violence and its perceived legitimacy -- its normalcy, its acceptability, the wide recognition it receives as either an overall positive or a necessary evil -- because the state is always an excuse for violence and because the more people think about justifications for state violence, the more likely they are to reject them.
The sudden disappearance of states is also a not-gunna-actually-happen hypothetical. Which is important because you don't have to actually worry about it, other than as an intellectual exercise. I don't mean states won't disappear some day, just that it won't be a handful of anarchists taking them apart in a series of coups in our current violent culture, for example, and then having to face an orgy of violence and think "what have we done!". So it makes no sense to talk like members of a committee planning a group action and expecting to reach a set of goals. "Hey guys, what do you think will happen when we set up our anarchy?" There is no downside to arguing against the state. These arguments are not actually going to unleash chaos.
I guess if you really think violence is unalterably hard-wired, you still have problems with a stateless world and with even arguing towards a distant one. Fine. Maybe you're Freud painting the superego as a good cop to the violent id in all of us. The state keeps us in check.
But no, I say, violence makes people more violent. Freud's superego, a product of parental violence, makes people more violent. Freud was horribly wrong.