What is the term for trying to shut down other people's contributions, which might be contrary to yours, before they even speak? I've seen it many times: Fabri

What is the term for trying to shut down other people's contributions, which might be contrary to yours, before they even speak? I've seen it many times: Fabricate something, attribute it to hypothetical commenters, and then disparage it. There must be a term in the world of rhetoric. The first part is essentially a strawperson.