Straw-man advocacy is a propaganda technique in which opponents of a particular position pretend to argue for that position using especially weak, ineffective, or foolish arguments, i.e. straw men, so as to lead uninformed onlookers to assume that the given view is only supported by weak and foolish arguments -- and therefore to dismiss anyone arguing that view regardless of whether they may have strong or valid arguments to support it.
It is a form of false advocacy.
A related technique often used in the mainstream media to discredit a position is to focus discussion on only the weakest arguments for that position. For any given position, it is generally easy to find people who will sincerely put forth absolutely terrible arguments for their position, thus providing real live "straw men" to attack in a believable way.
also known as: Straw-man packing, referring to the idea of "packing" one side of a debate with straw-man advocates
One major example of this technique is the widespread straw-manning of the 9/11 truth movement; there are probably others, however.