As of this morning, YouTube is opening fine on the different connections that I have tried. The ban has been lifted and the offending video(s) have presumably been removed (looks like they could have just asked YouTube to remove the objectionable content).
Whatever the motives of the ban were or what long-term effects it will have on Pakistan, at least this incident showed how vulnerable the Internet is and how even a clueless engineer (I’m sure it wasn’t intentional) in somewhere like Pakistan can bring down a website as big and global as YouTube.
This article (thanks Stuart) explains what happened when the PTCL/PIE guys attempted to block access to YouTube for Pakistan, but ended up blocking it for everyone else.