Sometimes it seems they are more like problem-relishers rather than problem-solvers, dwelling on every aspect of misery, inconvenience, and strife of the situation("We're all going to die..and it's your fault!!", rather than "How did this happen, and what can we do to fix it").
It's very hard to make them happy when they are in this mood. I think arguments for them isn't so much about figuring out a problem or making a point as it is about them indirectly asking for some kind of emotional support(no idea what that would be, probably differs from person to person). This paragraph is purely speculative, and I might be wrong.
If you deal with them calmly and logically address the problem like a T would, they won't accept they are wrong. Instead, they will go outside and try to undo the lugnuts on their tire with their teeth to keep themselves in a frustrated and determined despair while they contemplate their next campaign. Their ability to dodge reasoning like Neo dodges bullets, and to re-introduce even the most overinflated of insignificant events that happened years ago, allows them to have epic arguments. Much like a D&D game. As I said before, their arguing isn't always means to an end as it is with T's, but rather a request for emotional fulfillment of some sort.
Thus arguing will get you nowhere with them. Attack the root of the flame, rather than the flames themselves. In fire theory, a fire needs 3 things to burn. Fuel, oxygen, and heat. So, consider fuel as an idea or object that they can obsess over. You can't really cut these off with reasoning, as they will fabricate more. Heat could represent the emotions that react with the fuel. That is where you need to address them. You could cut off their oxygen supply, but that could cause brain damage, and will cause the fire to explode into an even more violent inferno when the oxygen is reintroduced to the heat and fuel. Trust me here. My dad tried it. It only got him arrested, and then the argument continued over the police telephone.
Unhealthy ISFJ=self defeating to the max.
I think you can add general neurosis to the list as well.
No need to thank me here. Just be appreciative of the misfortune of my having an intimate knowledge of unhealthy ISFJ's. :p