motte and bailey

The predecessor of the castle, having a raised earth mound (the motte) topped with a tower (or donjon), and a wooden ring fortification surrounding a courtyard (the bailey).

A form of argument and an informal fallacy where an arguer conflates two similar positions, one modest and easier to defend (the "motte") and one much more controversial (the "bailey"), by advancing the controversial position, but when challenged, insisting that they are only advancing the more modest position.