Yes, blatant. He clearly put a hand in the chest of the defender and used that to create separation. That is, by definition, offensive pass interference. Doing it in the end zone and right in front of the ref just made it all the easier to call.
Blatant? Yep. I agree. He clearly pushed off and created separation. Would every official call it? Perhaps not. But it was, by definition, a penalty.
The defender was grabbing the reciever. If you were going to make a touch call, it was defensvie pass interference. Of course if you weren't watching when the intial contact was being made by the defender, you could call the offensive interference.