Repressed memories are not that crazy. As we go through life, we collect thousands upon thousands of memories, and so they can't all be at the forefront of our conscious mind 24/7 or we wouldn't be able to function at all. Most of the time we have to focus on the here-and-now to be able to function, only recalling memories if they serve some purpose in our current situation.
For example, say you were walking around in a store that had music playing, and it suddenly played a song that you hadn't heard or thought of in years. Hearing it might activate your memories of that song from years ago. You might think, "WoW I forgot all about this song, haven't heard it in years!" But the truth is that the memories of that song were always there, your brain just had no reason to activate them until prompted by the music in the store.
Moments like that demonstrate that
1. the brain can choose to keep memories away from your conscious mind, if for no other reason than to not burden you with excess thoughts
2. the brain can pull up memories long dormant when prompted
Therefore the notion that the brain could choose to keep some memories from your conscious awareness, for your own good, is not crazy. The brain already does this in another way by selectively pulling up memories for you based on the current situation. You don't walk around thinking, "My phone number is.. my phone number is.. my phone number is.." But if you needed to write down your phone number on a job application, your brain would fetch that memory for you right away. Our brains are pretty flippin smart and amazing, really.
With repressed trauma memories, there is scientific neurological research and evidence that shows how trauma literally damages the brain organ. Because of this, under very severe stress, certain parts of the brain will actually shut down, stopping the incoming stimuli and processing, in order to protect itself. When this happens, our ability to comprehend what is still coming through is limited. For example in some cases, our brain might have recorded the visual information, what we were seeing, perhaps also audio, what people were saying, etc, but without processing any of it. Then the brain does have the power and advanced functioning to recognize that should those memories remain in the conscious, the brain would have to remain in a permanent state of being partially shut down, which would make survival very difficult. So therefore the brain must put those memories in storage with all of the other memories, and never activate them.
However, those memories are there, and so there is always the possibility that they could be activated if prompted in certain ways, under certain circumstances.
