I'm sorry, perhaps I wasn't clear.
Do you know of any successful court cases like this? "Successful", meaning the court found against the person who wrote letters of reccommendation?
Unless you can point to one, then the suggestion that this is unconstitutional and illegal seems to be unfounded.
You will lose this point unless you can show prior examples.
But don't let me stop you, go right on thinking that state paid employees using state resources can state they will discriminate based on race, religion, creed, or sex.
In fact, just test it. If you are a public employee, just state on your public website that you will not hire or promote creationists. Let me know how you make out.