These almost universally become this trope if you think about it more deeply. Consider individuals with coprolalia or copropraxia, for example. Somebody who keeps swearing and hitting others while stating that (s)he likes them and would never hurt them. This may look like Black Comedy at first... Until you realize that they are doing this involuntarily and have little control over it. And that they are likely to be very lonely people because of this. All people around them either (1) hate them, (2) laugh about them or (3) feel honest pity but nevertheless keep their distance because they don't want to get insulted, beaten and so on.
Some disorders also cause a lot of Fridge Horror to the sufferers themselves. E.g. living with Asperger Syndrome often includes being Innocently Insensitive to others. If the victim shows no overt sign of offense or other discomfort, you may do this merrily and only notice much later what a jerk you really were. Even worse with psychosis: You do weird, embarassing and potentially horrible things while being convinced that it's the right thing to do, or your only option at all (or that some evil entity does it through controlling your body). Afterwards, when you are mentally sane again, you may still have a detailed memory about it and start realizing what really happened and what you have actually done.
And the worst about these examples is that such situations can sometimes be downright funny to observe as long as you are neither the one who screws up nor the victim. And for the victim, it's often a good reason to hate the unintentional offender.