I don’t get the elitism or why you think someone with a degree from a specific school is inherently stupid. That’s as weird as refusing to hire non-formally educated people.
Harvard is good for signalling, traditional liberal arts, and pre-law (but, I repeat myself). It's not a very good teaching university overall, and especially not in CS.
That said, I think you’re completely out of touch with how 18 year olds choose universities. It can be as simple as a friend of theirs is also attending, or the school is close to a parent’s home, or they were actually in a liberal arts program before they switched into CS.
Sometimes as you implied, it’s their parents making that decision for them.
There’s no point in holding the cost of a student’s education over them, especially as you don’t know even how much they paid.
It's not reasonable, those statements are liability for you and the company you represent. Hiring laws are quite strict of discrimination.