1. There is no such thing as face guarding in the NFL (or the NCAA for that matter).
2. The reason Pereria and others felt it was DPI was that the defender never played the ball, and contacted the receiver. Yes, he was between the receiver and the QB, but he never faced the QB or the ball, he ran over the receiver when the receiver slowed.
3. Whether it was or wasn't DPI isn't even the point. The mechanics of throwing the flag, ANNOUNCING the foul, THEN picking up the flag with no explanation was horrible mechanics.
The Referee has acknowledged he may have acted too quickly in announcing what he BUTT/u/med was the call before recognizing there was a differing conclusion. However, once recognizing the possibility of a dispute, he consulted with his crew members, got their input and made a decision (presumably) based on that input to get the call (what they believe, RIGHT).
As might be expected, or at least anticipated, some TV announcers and a bevy of arm chair experts, given the advantage of repetitive replays, opinions, assessments (right and wrong) disagree producing the still (and hopefully long continuing) impact of "So what", as the game continues on.
Total perfection is a laudable goal, but an ever elusive objective. If all the arguments, disputes, challenges of decisions were somehow removed from the game, would it remain as popular and as enjoyable?