It is a pen, but you cannot determine a red card on the basis of a still frame. Even if it was intentional, which I don't for a second concede it was, a referee cannot prove intention from a still frame, and consequently cannot make a determination on the basis of it either. A still frame can prove the ball has touched his hand, but it cannot account for split second movement, original body position or even direction of movement of the arm just prior to that still frame without an actual video replay.