If this "slavery banning" would really be a thing, should I put my carriers for friend / squadron use only, so nobody can land their alt on my carrier, and when I go out exploring claim that I have kidnapped him (even though I would not even know he is on board of my carrier)?
Unlikely, unless there's evidence of deliberate recruitment - and entrapment - to un-navigable systems. Now the Galnet article is out there, people have been warned the risk of docking with carriers, so you're covered re stowaways for sure.
I'm also sure there will be a permanent flag to that risk, put in the game somewhere, pretty soon too. Slavery will probably stay highly illegal untl Devs can be sure new players can easily find out how to get off carrier and some way to find and dependably flag slave ships is figured out.
Quite a bit of this might seem a bit grey area but I think it's pretty clear what counts as unacceptable behaviour when you think about it. It's really the same as setting trade prices in carrier commodities .. enough to make a profit yes but also low enough to attract people to haul for you. There is a just profitable sweet spot in there but carriers aren't (and I don't think should be) a license to print money. if you want people to work for you, have to pay them fairly and provide reasonable work conditions.
What did Sting say when shadow banned to solo?