I just saw a 3 hour long music mix on Youtube with a definition of "Fair use" (link related) in the description which didn't apply to a single second of the video with the standard "no copyright infringement intended/I don't claim ownership/etc." tacked on for good measure. I realize there are a zillion videos on Youtube like this but it's just a pet peeve of mine.

No, it's not the copyright infringement that gets me (it was a great mix btw)...it's the part where people are clearly stating they understand the definition of fair use and copyright and are basically admitting that they are knowingly violating those copyrights.

That isn't a legal disclaimer. In fact, that's worse than no disclaimer at all because if there was no disclaimer, you could at least say, "Well...duh...I didn't know." Instead, you're drawing direction attention to the fact you're infringing copyright and admitting that you're fully aware of it.

I saw a post where someone made a parody of the film Titanic and used the soundtrack in their film which was subsequently taken down on Youtube. Making a parody film still doesn't give you rights to a complete copyrighted soundtrack.

That's not to say that Youtube and content owners/managers haven't been guilty of a massive amount of heavy-handedness and over-stepping bounds themselves specifically with Youtube's mostly terrible Content ID system. You might remember AngryJoe's incredibly angry rant about Youtube's Content ID system. Those are definitely legitimate examples of fair use and legitimate concerns.

But posting hours of copyrighted music? No. Knock that off. Well...except for this music mix I'm listening to right now, it's pretty good. All I'm saying is stop putting disclaimers on your videos that basically state, you're completely aware that you're violating copyrights.