[4bpp]

The difference is that all the unhabitable land on Earth is still nominally owned by someone, and human society has committed itself to treating these claims of ownership with a lot of respect. Modulo a few famous and very small exceptions, even stretches of hundreds of square kilometres of empty desert far inland belong to some country and building an earthbound sovereign "Mars base" there will quickly result in missiles and dudes with guns raining down on you with the full backing of the international community.

Hardly anyone who suggests that the racists move to Somalia believes that the racists, after doing so, should be free to take over the place and rule over, displace or genocide the Somalis. Conversely, if this offer were actually on the table, I'm sure plenty of racists would step up to take it.

[ben_w]

The ability to build a Mars colony is not the same as the ability to seastead, but there is some overlap. I suspect that the 2/3rds of this planet currently treated as international waters would become habitable on a similar schedule as a Mars colony.

Not that I have any reason to believe racists can be convinced to go away no matter where or how appealing the destination is. If anything, I would expect the contrary.