I take it you've never played the game at any level? When you fly into a tackle or move to block a ball, or even jumping for a header, your arms and hands move to positions which aren't 'natural'.
You cannot run around a pitch with your hands and arms down by your side. The force in which the ball was struck also made it impossible for lasley to do anything about it or even attempt a block with his hand. It was never a penalty imo.