That sounds apocryphal. That looks like an outtake from Ghosts, which was filmed in 1996. Yes, "Is It Scary" was originally released in 1993 as part of the Adams Family Values soundtrack, but as far as I know there was no music video filmed for it. Even an unfinished one. It was later included as one of the songs in the 1996 Ghosts short film.

If you haven't seen it, in Ghosts Michael plays a kind of eccentric aristocrat figure who lives alone in this old creepy castle and the people of the nearby village (Michael also plays one of them) want him gone because he's creepy and they think he scares the children. So that clip definitely looks and sounds like an outtake from that film. Maybe he channeled some of the rage from the 1993 allegations, and the plot certainly does seem to be an allusion to what he went through in 1993, but he didn't learn about the allegations just before the scene or anything like that, and I doubt it was an unplanned outburst. I think it was a planned scene but they cut it for whatever reason.