On top of that, unless I missed something, the documents I've read excluded engineers, the ones getting their jimmies ruffled, from the 'do not hire' list and simply had them on a 'no cold call' list. It was management and sales that were under some 'do not hire' list, right?
In this whole thing, the only part that I find morally/legally suspect is the agreement to not hire certain categories of employees from certain companies. Everything else is just a bunch of hand waving from highly paid people that want to be paid even more. And even that, had it been worded slightly different, would be arguably legal.
I (as an engineer) have my "jimmies rustled" because this sets a really worrying precedent for the behaviors of these companies I do/might work for, and is frankly the sort of behavior that makes me have implicitly low trust for people with this sort of power, which is an unfortunate state of things. (I'd really like to be able to trust people, I promise...)
Focusing recruiting, sure. But pre-filtering on the basis of factors "not relevant" to the person performing the job starts to get into a very grey territory in terms of discrimination. (I realize on the surface this seems silly since where you are working is totally relevant to a new job, but not in the context in which it was being utilized.) I really don't intend to draw a strawman with this, but that I see a big difference between their limiting their effort, and their prohibiting your effort.