The point of the reference to Plato is that in his writings Socrates establishes a bare minimum that we should expect from a legal system if we are to respect it. Being able to leave isn't sufficient, however it is necessary.
When states start revoking passports to restrict the movement of people under their jurisdiction, they fall short of something that we should respect.
No, I got it and I don't think there is anything particularly wrong with the point itself, per se.
The basis of the point, though, is one report from an advocacy source - and here we are talking about the moral philosophy of law and statism and the Prussians and Plato. Meanwhile nobody's actually found and referenced another report of any kind. Maybe from German media. Maybe a publicly available court document. Anything.
This sort of anti-pattern makes me think that stuff like this should be mercilessly flagged off the site. If you're particularly keen on talking about it, write it up, as soberly as you can, put up some links and post that. Linking the advocacy post itself is near-guaranteed to generate almost exclusively heat at the expense of light.
When states start revoking passports to restrict the movement of people under their jurisdiction, they fall short of something that we should respect.