The Motte and Bailey

The “motte and bailey” is a sort of argumentative sleight-of-hand. The offender starts with a weak, controversial position, known here as the “bailey.” When the weak argument is criticized, the debater switches to the “motte,” and a strong, uncontroversial opinion that’s harder to argue with. It’s a moving target that sneaks nonsense in with positions that everyone can agree on. It goes something like this:
Bailey: “Fast food should be outlawed to fight obesity.”
Counter argument: “Shouldn’t people have the freedom to choose what they eat?”
Motte: “Don’t you think we should promote healthier eating habits? We’re facing an obesity crisis.”