hmmm... Well I not saying that you shoul keep the EQ flat when tracking all the time, but the resonig behind this is that you shoul try to concentrate on making the source sound the way you want it from the beginning (i.e. through mic placement and good acoustics etc...) Lets say that you are micing a guitar amp, you set it up and audition it, and you decide that it need a little more bass. You should try to achieve that through mic placement or on the setting on your amp before you go boosting the signal with the EQ on your mixer. You want to get as clean a signal as possible to taPE, adding or even cutting EQ will put some (not very much, but some) sort of distortion on your signal and distortion = noise. In certain situations however, this can be a good thing, it's all very subjective, but as a rule of thumb, if you want the cleanest and most trasparent sound, the less that you do to the signal to closer you will get to achieving that.
-jhe