So, by this logic, the stated reason for the Southern states may have been self-determination, but it really could have been to keep slavery.
My position is that a right is not contingent upon your reasons for wanting to exercise it.
Our right to freedom of speech is not constrained such that we only have it for approved speech. We have the right to say things to which other people disapprove.
In the same manner, the right to independence is not contingent upon approval from others. If you have a right to independence, you still have a right to independence even if you have bad reasons for wanting independence.