You're wrong on a couple points. First of all, it's not entirely about stopping violent crimes. If that was the case, it would simply end after a determination that the person didn't have weapons. But in the majority of instances, they rifle through every little thing in your pockets looking for drugs and interrogate you about your activities. Even the small percent of stops that lead to an arrest are overwhelmingly for petty drug possession charges. And further, they wouldn't engage in the despicable tactic of telling people to empty their pockets and then elevating the charge to public display of marijuana, something that continued after Ray Kelly "ordered" them to stop.
Second, calling them "terry stops" is not accurate. Terry requires them to be able to cite "specific and articulable facts" that give them reasonable suspicion to believe the individual was involved in a crime. Also, Terry limits the search to the outer garments solely for the purpose of checking for weapons for officer safety. As noted above, this is not the case. 780 guns from 685,724 (2011) isn't limiting themselves to this standard.
Also, the evidence is quite clear that they have quotas on how many of these stops they have to make. How fair do you think an officer struggling not to get reassigned to traffic duty is going to be? Is he really stopping people to help end violent crime?
And just to add an anecdote, I used to routinely conduct business on a block with one of the highest stop and frisk rates in Manhattan, in East Harlem. But I'm white and clean cut and well dressed. I was never been stopped in over a year of just standing there for 20-30 minutes 3 times a week. And the majority of white people in the neighborhood are there for a particular reason, but I wasn't profiled.