The Raptors allows other clubs to hit 38 per cent of their three pointers, tying them with four other teams for worst in the NBA in that category. Just for comparison, the Phoenix Suns make 38 per cent of their three-point attempts, and rank fifth in the NBA. Right now the Raptors are turning every team they play into the Phoenix Suns, at least from the three-point line. That kind of defence negates any advantage the Raptors have from the three-point line in a hurry.
Why can't the Raps defend the three? I'd welcome all explanations. But here's one possible theory: The Raptors rely way too much on help defence from their perimeter defenders. This was really evident against Cleveland and in the game against Phoenix at the ACC a while back.
When Lebron or Nash drove, too often, a Carlos Delfino or Jason Kapono would fall off their man trying to help out, and it was all-too-easy for LBJ or Nash to simply kick it out to the open man for the three. The Raptor defenders need to be aware of who they're covering and plan their help defence around those assignments. If you're covering Damon Jones or Rasheed Wallace, sorry, no help from you. If you're covering Devin Brown or Jason Maxiell, go right ahead.