Because of this, you should select a major premise that is fairly uncontroversial and that will be accepted by the judges and perhaps even by your opponent. Few people will take issue with the claim that slavery is wrong, or that theft is wrong. If, then, you can show that your conclusion follows from such claims, the moral underpinning of your argument will rest on secure foundations. Your basic strategy here is to show that your conclusion follows necessarily from a well-established moral principle. This can be a powerful debating tool and often yields surprising results.
Theft is the appropriation of property without the owner's consent.
Taxes require the appropriation of property without the owner's consent. Therefore, taxes are theft. Taxes are theft. Therefore, taxes should be abolished. From a simple definition of theft in the first syllogism, you have arrived at a surprising conclusion.