The irony in this post is of all people you choose to mention, he is a big advocate of utilizing Glucocorticoids around workouts..
You are absolutely right, it is a necessary hormone, evidence suggests that there is a correlation between acute responses to resistance to training and greater increases in lean mass. (Invalid Link Removed).
Cortisol isn't like insulin which has acute effects by binding to receptors on the cell surface eliciting immediate effects, it is more comparable to hormones like testosterone which operate at the DNA level as a transcription factor which binds to specific sequences of DNA to either increase or decrease their rate of transcription to mRNA. So people need to stop worrying about acute spikes in cortisol, because it likely isn't relevant in the scheme of things, its simply the body reacting to a stressor to get from "A to B".
Besides my comment in relation to this person training after work, using a pre-workout at 5pm for training doesn't translate into disrupted sleep? we don't know his tolerance? both of you are making blanket statements that may or may not be relevant to this person.
I also train in evenings and use stimulants every, single time. But i know what amounts my tolerance allows and still sleep like a baby despite the "unwise cortisol spike".