Ummm...your not flushing out a bad taste, your flushing out your build up of nutrients, forcing the plant to use up it's reserves to get all the clorophyll out, or as much as possable. I'm sure you have had the unfortunate time or two of smoking something still full of chlorophyll...you get that lip and tongue burn? Happens alot with weed that has not been flushed or cured properly.
I do agree that if you are growing with living organisms "TLO" it is counterproductive to flush. You will only be washing out what you worked so hard to build up. Other than that there is nothing harmful in doing a flush.
When I do a midway flush, I wash out all the veg nutes that may be stored in the soil, and right away add my flowering nutes....all I'm doing is not allowing my plants to take up anymore of the high N nutrients. I have never had any form of shock from a flush. The leaves are always still standing tall. But then I don't get a noticeable shock from transplanting either like I hear so many talk about.
Like I said...I'm not trying to convince anyone to flush, I could care less what you do with your grow, but at the same time I'm not going to stop flushing either, because it's the way I do things, and the way the guys I learned from did things for many yrs of indoor growing. I guess my oppinion of it is, why would so many of the grow guides suggest it if it weren't important?