No. Not all failures are fair. Sometimes we can fail through no real fault of our own, simply by bad luck.
Look at sports, for example. There are any number of ways to fail in a sporting event that are not your fault. You can step on a wet patch on the basketball court and slip or a sudden gust of wind can come up and knock your golf ball into the water short of its target.
Even in the "real world" the same type of thing can happen. You can go to an interview and it can just so happen that one of your interviewers is in a bad mood and does not like you even though you do well in the interview from an objective point of view.
Because these kinds of random things can occur, not all of our failures are fair.
I do not feel that all failures are justified. However, I do feel that all failures should be learning experiences. When speaking of academic failures, I think that sometimes an instructor may have lower teacher expectations for a student. In that case, she may not grade the student fairly. Each student should be considered an individual and the instructor should consider both background and ability. It is the instructor's job to assess prior knowledge and try to close the gap between what is known or unknown. As an undergrad, I received some grades that I did not always consider fair; however, I learned from them. I went on to graduate school; eventually earning the doctorate. I feel that all students can learn; there are varying levels of ability. The instructor must be willing to adapt; she must be willing to consider her instructional delivery; such that every student might benefit.