Actually, I think we all got your point. Some people appear to be quite happy to accept that mistakes happen and don't seem to fully comprehend the significant difference in the acceptance that they happen and fighting tooth and nail to avoid them in the first place.
However, I don't think you realised you also made another point. Poor training and supervision means that errors will occur at times when they shouldn't. Fantastic that you're passing that lesson along but the system has failed if it allowed you to make that particular mistake in the first place. It's not like we haven't seen that error before.