Were these bureaucrats just waiting in the wings for an excuse to pounce
    with regressive policy?

Yes. American culture has always been a tug of war between puritanical norms and libertine norms, and we're seeing the latest mutation of the puritans taking over. It doesn't seem that way, because this iteration of the puritans have co-opted the language of the libertines, but if these university administrators were transported back in time, they'd be enforcing Prohibition laws with equal zeal. Transported further back in time, they'd be organizing the expulsion of Catholics, Quakers and other "heretical" religious sects. There is, and always has been, a large segment of America which looks at the average frat kegger the same that a Taliban mullah looks at a collection of unveiled women. They hate fun, and, given a chance, they will do their utmost to banish it. And if fun can't be banished, it will be regulated into submission.

Of course, they don't do this for themselves. No, of course not. They do it to improve the moral worth of the people. Their zealotry is driven by the purest of intentions.

    Who decides who has sour grapes?

The ones who have placed themselves in a position to define which grapes are or are not sour: the aforementioned bureaucrats.