Still, I would like to hear your thoughts on why racing during base training is so detrimental.
I don't think it is so I can't say for sure why one would say it is. In fact, I can only think of only one plausible reason why some people might think so off the top of my head. If one were to spend time tapering and recovering from a race, that would cut into your base training time and be detrimental. However, when I train through a race, an easy day the day before and the day after is about all the taper and recovery I take. In fact, during base, I usually don't change any plans except for race day.
The things I read last week indicated that one hard effort would equal the end of base training and that you would basically be starting over with base training after that. To me that just doesn't make sense.
It doesn't make sense to me, either. I do remember a statement from one of Lydiard's writings that, once you commit to beginning a race prep phase by doing an intense workout, you are best off following through with it or starting over. However, I don't think me meant that one hard effort, whether workout or race, during base training meant you have to start from day one. I think his point was more along the line of telling people not to mess around for months on end with occasional workouts and instead to condense them into a period of 2-3 months going into your goal race. That doesn't mean you can't do the occasional race.