You could put a small note on that custom twitch UI you built to say that the stream reflects your personal work and should not be regarded as a professional tutorial. Something like that with better wording. Also I think this is a one time thing (kind of). If they did that to the Bliss or Morrigan streams the "tutorial"…
I do this already with streaming some games, there are casting programs that allow you to overlay and show only what you want (for example only show Zbrush and not the 'images' you're looking at in the background) overlay/add images to the steam and also add other looping videos/webcam inset into the stream before it even…
I have to say, this kinda shows that you are on the map, you're popular enough that people want to rip a stream and upload it as tutorial based upon name alone. At the same time however, lets face it, most likely the person who did this did it for the sake of generating cash via downloads, these peeps will rip anything out…