As an isolated play, I didn't think it was a cheap shot. Flagrant II for sure. However, while watching it I was reminded of the play on Sunday where Dirk swung his arm around "reaching for the ball" and clocked D Fish upside the side of his head. Isolated, I thought that was a Flagrant II as well just because of the hard contact with the head region. Put them together, two games in a row and maybe he is playing a little dirty. One can definitely see that part of the Mavs improved D is playing more physical. Clearly, Avery Johnson, or someone in the organization is coaching the Mavs to be "tougher". They've been called soft for so long, I don't blame them. I'm all for physical play and have never been one of those fans that cries foul when teams get physical. Rather, I expect my team to step up and match the style of play.
There is a fine line between playing physical and dirty. I believe that in this case Dirk might have crossed the line unintentional simply because it's constantly being beaten in to his head that he's soft and needs to play tougher.