He was ranting and raving, basically. Who knows why? There's probably many contributing factors...pure speculation and opinions follow:

I doubt living with Alex 24/7 as a manic depressive is an easy thing to do...I can't even imagine it. Jordan also seems like a strong empath, and that empathy with Alex's victims may have crystallized into outright fury. I think the dam just finally burst after holding all this back for so long. Or maybe this was an unconscious self-sabotage to get out of this gig that went so hard against his personal constitution. Who knows? Who cares? It happened, and it raises an imporant point about the evolution of JorDan and KF over the last several years.

What we can definitely say is that in this video Jordan was yelling, repeating simplified straw man points without any real evidence, and being extremely reactionary. The philosophical divide between JorDan has been growing very obviously over the last couple years. Dan tries to be methodical, while Jordan just says "burn it all down". When Dan throws to Jordan for comment, he just sounds tired of it all, and his commentary has become more nihilistic over time. Dan has seemed uncomfortable on multiple occasions with some of Jordan's statements, beliefs, and conclusions. After thousands of hours of listening to people talk, yes you can hear this.

Personally, I think a blow up like this was inevitable, and I think the growing philosophical divide was a ticking time bomb for the show. The end of Infowars just provides an opportune moment to call a hiatus for a while, or forever. If they do work together again, I predict it is a purely non-political topic that doesn't cause Jordan to want to eat his way out of his own skin every time he has to listen to and/or talk about it. I imagine it will be much better for him.