Maybe what you meant is that fair use is an affirmative defense...? It will win a case for you, but if a rights holder is determined to take you to court over it then it won't immunise you from the hassle of a court battle and most content platforms will acquiesce to the takedown in the meanwhile. This has all supposedly changed a lot in the last 10 years with hosting platforms being asked to 'recognise fair use' more, although idk exactly what form that has taken. I don't think it's been tested much since devs have mostly stopped worrying about it.
Maybe what you meant is that fair use is an affirmative defense...? It will win a case for you, but if a rights holder is determined to take you to court over it then it won't immunise you from the hassle of a court battle and most content platforms will acquiesce to the takedown in the meanwhile. This has all supposedly changed a lot in the last 10 years with hosting platforms being asked to 'recognise fair use' more, although idk exactly what form that has taken. I don't think it's been tested much since devs have mostly stopped worrying about it.