Sure, you could make that argument. As I said, I think there is enough wiggle room that it should have been left up to Congress, which would mirror your point about the Indians.
But you can't credibly argue that the Supreme Court simply ignored the "and subject to the jurisdiction thereof" clause as that other poster claimed. The Court very clearly pointed out the diplomatic immunity exception still applies.
The Amendment was poorly drafted, and the decision could have credibly gone either way. It didn't go the way I wanted, but unlike some other wacky decisions, there was at least a reasonable argument to be made for the way it went.
Rereading your post... yeah that is exactly what you said.
In my defense, am I not supposed to get up and arms over posts on the internet after misunderstanding them through no fault of the poster? I think that's how the internet works.