The hit came early in the game, before either team had even scored. The Capitals were cycling the puck from behind their net in the defensive zone when Rempe came in and finished his check on the Capitals defenseman.
Many fans were not happy with the call. After all, Van Riemsdyk was the last one to play the puck and Rempe was already committed to making the play. Perhaps he hit him a second after the puck was gone.
That being said, other fans had quite the opposite reaction. In fact, some feel that the hit was dirty enough to warrant a suspension.
Perhaps the fact that the reaction from the fans is so varied in this case is evidence that the referees got the call right. Obviously there are going to be extreme opinions on both sides, but the refs made a 'middle ground' type call with just a minor penalty. You can be the judge of the play for yourself.