Sometimes, you try as hard as you can, but you just can't beat somebody.
Will Beatty blocked Jared Allen. He used his arms to keep one of the league's most vicious defensive ends in front of him. He did not commit holding.
But he got backed up a little bit, a lot actually, until he was close-ish to Eli Manning, and Allen was able to sneak his arm through Beatty... and sack Manning anyway despite being completely blocked.
Of course, Allen is helped by the fact that Manning kinda goes into a shell like a turtle when the defender gets his paw on him, but I probably couldn't escape from a clenched Jared Allen fist grabbing my shirt either. And somebody else comes in to clean up the play.