I met up with the tenant yesterday to collect the security deposit and the portion of this month's rent that they are paying. After two kisses on the cheek, he apologized. He said that I was totally, totally right. It's just that they were going through a lot - I guess this move is especially stressful - and they were too far into their problems to be able to see anyone else's point of view but their own. Once he thought about it, he realized that they were being unfair.
They had apologized before for blowing up, but made it sound as if they were paying this month's rent just to appease me. I feel much better after this