Former Texan here. Bring up the fact (and it is a fact) that the creation of Texas and its subsequent fight for independence was 100% slavery. Enjoy the fireworks.
Texas "was received as a commonwealth holding, maintaining and protecting the institution known as negro slavery-- the servitude of the African to the white race within her limits-- a relation that had existed from the first settlement of her wilderness by the white race, and which [Texas] people intended should exist in all future time"
Gee, what a hard question to figure out from historical sources, guess we'll never know what they were thinking...