This isn't about anarchy; it's about competition. The thing to keep in mind about governments is that people tolerate their abuses because they provide certain services (protection, property and contract enforcement, etc).

The fundamental idea of Seasteading is that land creates bad governments because the cost of changing providers is prohibitively high. So you end up with a monopoly provider over a certain area that generally becomes wildly inefficient and corrupt (in the sense of institutionally violating the rights of individuals).

No one in the libertarian movement denies the need for someone or some group to provide the services of personal and property right protection, "rule of law," contract enforcement, and whatnot, but if you use the same creativity the people here would apply to any other industry, you clearly see that there must be a better way than what we have now.

That's all anyone is looking for.