Horde Griefer Cevo (video)

So guy named Cevo some horde mage is mad that I am in the same area as him so he decides to spam sheep the mobs I am trying to kill. It's quite annoying so I decided to capture it on my video camera. WTF is this crap and what can be done.
https://www.youtube.com/watch?v=FgHohQV ... e=youtu.be
https://www.youtube.com/watch?v=FgHohQV ... e=youtu.be