If he thinks there is a penalty called "face guarding" in the NFL, he's wrong. And if he thinks you can be called for any type of pass-interference-like penalty (whatever someone might choose to call it) even if you don't make contact, he's also wrong.
If you're not looking for the ball and you MAKE CONTACT with the receiver, that's pass interference. Some people might erroneously call it "face guarding," but the penalty is for making contact, not for getting in the receiver's face or blocking his vision or whatever. That's the bottom line. No contact = no penalty, no matter what. If there was no contact on that play, it was a bad call.