I've noticed that too and I think it comes with his reputation, but also the reputation of his team. I don't know if you've noticed, but the refs let the Pistons and the Spurs play much tougher than they let other teams. Why? Because the Pistons and the Spurs are tough. Their defense does not arise from angry retaliations due to failed offensive plays. It's who they are. So, the refs know that Bowen is a great defender and have witnessed it over the years so they let him play his game. Aside from the bruce lee kicks here and there, he doesn't do anything that really obstructs the rules. However, you could argue it's borderline. Still, the main reason why he's labeled such a dirty player by scorers like Ray Allen and Kobe is that 78 games out of the season, Kobe and Ray face similar and mediocre defensive players, with some exceptions. Therefore, they are accustomed to what defense should be. When it comes to playing Bowen, they hit a concrete block.