I don't get the antagonism.
When someone says they want to be free of the rule of national law that might mean they want to violate a law that I generally support. Maybe they want to provide untracable anonymous phone numbers to robo-calling telemarketers, or tax avoidance services to shady billionaires, or subpoena-proof corporate records for companies running unsafe chemical plants.
That has the potential to be antagonizing - although the potential is not yet realized.
Maybe the fantasy is impractical and nothing will come of it. On the other hand, maybe these plans will create something new in this world. The American content was populated (invaded, if you prefer) by people who wanted to create different social organizations and were willing to take enormous risks to do it - this impulse is deep in our psyche.
Alternatively, look at it this way: It's an opportunity for you to look smug and say "I told you so" in a couple decades. Encourage it.
I like these seasteading projects. I don't imagine they are going to become floating Utopia but they might be _different_ and that will be interesting. Like Disneyland, you don't have to live there to want to stay a while.
I also think people are overlooking the primary benefit of something like Blueseed: It creates an urban density of talent that makes Manhattan look like rural Texas. I would love to build a startup in that kind of environment.