It was clearly calculated. He could've declared his next shot unplayable, gone back to the original spot where he last putted from, simply assumed a 1-shot penalty, and would've had a club-length to putt his next attempt.
He was clearly frustrated and wanted to make a statement to the USGA.
They weren't on the clock, they weren't holding up play. Phil wasn't happy with the setup, and although he has a lot of players who would support that opinion - he overstepped the line of integrity and the spirit of the game with his actions.
Had this been Pat Perez, he would've been DQ'd.
I love Phil, he's done far more good for the game than bad, but this wasn't one of his finer moments.