If you listen to the conversation, Deeb said he did it because he thought Matusow wouldn't take it seriously and take it as a joke. But he's an idiot. If they're there socially and having fun, then there's no reason to slow-roll as a joke. It's plain rude. Long time ago, I used to slow-roll a slow-roller and used to get kicks out of it because I used to justify myself that he deserved it anyways. But when I got slow-rolled, it was ugly and very disgusting to the point where if I had met that person in real life, I would knee the **** out of his face. Slow-rolling is not cool. I've slow-rolled slow-rollers, and been slow-rolled and learned the lesson the hard way.
Just recently, about two weeks ago or so, I've been accused of slow-rolling even though I instant-called and rolled over my hand right away after my villain rolled over his hand.
https://www.cardschat.com/forum/general-poker-13/slow-roll-show-your-hand-last-230539/
Even when I had no intentions of slow-rolling and just wanted to get information about the villain, I still got accused of slow-rolling just because I decided to show my hand only if my villain showed his hand first since last raiser of the river shows first.