Why did thomas f. drayton deny that the confederacy was fighting to defend slavery?

Thomas F Drayton denied that the Confederacy was fighting to defend slavery because he was worried that an invading Union army would enslave white southerners.

This fear heavily influenced Drayton's decisions during the Civil War. Drayton was appointed as a brigadier general in the Confederate Army by President Jefferson Davis. His influence in the Confederate Army began in September of 1861 but ended after his poor performance at the Battle of Antietam.

Do you have more info about it ? i doubt this is the answer because i don't have all the information but if trouble was brewing in a clinic maybe it was an argument as to which clinic was better or smth of that nature