And in that particular aspect, they are joined by some democracies, including, I would argue, even democratic India, that do not view it as the singular organizing principle of international statecraft.
1 Why not "even including, I would argue, democratic India"?
2 Can "that" introduce a non-restrictive attributive clause? I think the introducer should be "which".
Edit: I first thought the that-clause was a non-restrictive attributive clause modifying the noun which "that" immediately followed, i.e. "India". After reviewing, I noticed the verb is "do" not "does", so what the that-clause modifies is not "India" but "some democracies", and the that-clause is restrictive.