Unfortunately only a judge or jury ultimately gets to decide what's fair use, which means the person without the in house legal team is at the mercy of the person with legal resources regardless of who's right and who's wrong. Follow Steve's links above for the nitty gritty. This seems like an open and shut case of fair use to me, but I'm on the wayyyyyyy media hacky lefto archist side of that issue so my interpretation isn't what would necessarily hold up in court. In my world, unless someone's pirating (making money off of a copy of something as if you are the producer / selling something as if its the real thing when its not) or non-satirically making it look like you endorse something when you don't (which is libel so doesn't even fall under this umbrella anyway), the use should not only be protected, but get a little "Upholder of Free Speech" gold star. The Fair Use exception can be interpreted to be pretty close to that (minus the gold star of course) - unfortunately, it can be interpreted in the reverse direction too, depending on which of the evaluative factors listed in the law is weighted more heavily by those making the judgment. The DMCA muddies the waters further.
Brook _______________________________________________________ Brook Hinton film/video/audio art www.brookhinton.com studio vlog/blog: www.brookhinton.com/temporalab