You have asked quite a loaded question.
Legally, by using their song, you are violating their copyright (performance of a copyrighted work, e.g., by including it in a video you are publishing, is a violation of copyright, even if done for no profit). Even if you credit them as the creator of the work (which you should do!), you are still using their work without permission.
The legally correct path to go about this is to contact Deadmau5’s agent and work out a licensing agreement.
What seems to be the “socially acceptable” path is to just post your video, and it’ll be taken down by youtube if anyone reports the infringement. You may open yourself to an infringement lawsuit (criminal or civil), but that’s not terrifically likely, although you should understand that it could happen.