IANAL, but as appalling as I think they would be, MLK-Hitler posters are practically the textbook case of fair use:
1) Transformative factor: To say that an MLK-Hitler poster "adds new expression or meaning" to the original is to make the understatement of the year. I may not like the new aesthetics, but they are certainly there. Furthermore, the posters are powerful imagery (value is added) to those who hate MLK.
2) Amount: The posters only excerpt a single frame of a much longer video.
3) Nature of original: The video is not abstract art... it documents a historically- and culturally-significant event. This gives poster-makers broad latitude to do as they please.
4) Effect on market for original: Any argument that an MLK-Hitler poster is a substitute for video of the original speech is a non-starter and doesn't pass the giggle test. You would have to argue second-order effects, (that the posters ruin MLK's image, and therefore reduce demand for all things MLK) and courts haven't really gone for that (if they did, you couldn't publish an unfavorable movie review that showed a still from the movie). If anything, it probably inspires people to try to find the original and pay the (outrageous) licensing fees.
So an MLK-Hitler poster passes the fair-use test on every single count.
1) Transformative factor: To say that an MLK-Hitler poster "adds new expression or meaning" to the original is to make the understatement of the year. I may not like the new aesthetics, but they are certainly there. Furthermore, the posters are powerful imagery (value is added) to those who hate MLK.
2) Amount: The posters only excerpt a single frame of a much longer video.
3) Nature of original: The video is not abstract art... it documents a historically- and culturally-significant event. This gives poster-makers broad latitude to do as they please.
4) Effect on market for original: Any argument that an MLK-Hitler poster is a substitute for video of the original speech is a non-starter and doesn't pass the giggle test. You would have to argue second-order effects, (that the posters ruin MLK's image, and therefore reduce demand for all things MLK) and courts haven't really gone for that (if they did, you couldn't publish an unfavorable movie review that showed a still from the movie). If anything, it probably inspires people to try to find the original and pay the (outrageous) licensing fees.
So an MLK-Hitler poster passes the fair-use test on every single count.