I believe teens need a place to congregate and interact in a safe environment. I do not believe that environment is the local mall.
There is a mall on SR 50 in Ocoee, FL, The West Oaks Mall. It's nearly deserted directly as a result of gangs of teens marauding and committing crimes (personal attacks, theft, ect.).
Yes, unfortunately, I think that in those cases where teens have been shown to be a danger to the operation of the mall, and to the people who go there to use the mall for its original intent, their access needs to be controlled.
Of course, in a perfect world, in a society that truly cared about teens, there would be a viable alternative for their socialization.