In overtime, Petry decided to stop playing, and instead chose to "bicker" with an opponent. Remember that it was a 3-on-3 situation and that Petry was the only Penguins defenseman on the ice.
Result: By literally giving up his position on defense, Petry left the opposing team a two-on-none with plenty of time to maneuver, and in a surprise move, the Hurricanes scored the winning goal.
You could say that Petry was trying to defend his teammate, but still! He could have waited, and anyway, he didn't do it all year last year with the Montreal Canadiens (defending his teammates)