People aren't thinking this through. There are all kinds of blocked punts, from barely grazing the ball to full-blown blocks where the ball goes backward. The rule has to handle all these scenarios.
If the punt gets blocked and doesn't get past the line of scrimmage then the Vikings would have had to get a 1st down. Since the punt still got past the line of scrimmage, it's a punt following the rules of any other punt. Our player touched the ball and couldn't hold on it to it. That's a live ball, end of story. It's not a bad rule but terrible judgment for our player to try to grab that ball out of mid-air like that.