I'm not attacking your facts and your logic is just as sound as the pro-slaver's logic was. I'm also not saying that Scotland is a vassal state. I'm only saying that your entire premise is false.
The post you responded to stated that "I don't think you understand that you've not exactly treated Scotland very well and that's one of the reasons it wants to leave," to which you responded that Scotland was poor before and would still be poor if they were left to their own devices. The argument that self-determination can't be trusted to the Scots because you know better is exactly the same argument made in favor of slavery.
BTW whatever happens it looks like at least half of Scotland is going to disagree with it. So even if the vote is for independence, they're hardly "unwilling subjects", especially as they want to keep large parts of the union.
Many slaves in the US weren't happy about losing their "job" and being cast out on their own, so I guess they were hardly "unwilling subjects".