You make no sense. If the U.S. government, in which the Southern states were we well represented, imposes a protective tariff then that's grounds for secession. But if the Confederacy imposes a protective tariff then that's perfectly OK. Either a protective tariff is wrong or it's not. It's either grounds for rebellion or not. You can't have it both ways.
Of course I make sense. Did the south benefit from tariffs imposed by the Union? The south didn’t think so.
Would the CSA benefit from tariffs they imposed? Sure, if they set them up for that purpose.
Why would you think the south would be any less inclined to protectionism if they thought it to be in their interest instead of their detriment?