Well, one thing I may add to this discussion is this: We are still in the early stages of the ban on the internet. This situation is akin to the yeshivos not allowing children with a television into their schools in the ’70s. We don’t know yet how this will pan out (I personally think that the ban will fail, we need a more workable solution, but that is beside the point). In the meantime, not allowing the children into the school is too aggressive.
I think many people will agree with me that it makes sense NOWADAYS that some yeshivos do not allow children with a television in their home into their school. I have personally seen how a child with no television is adversely affected by the classmates who do have one. But that is because the stance on television is pretty well understood. The stance on internet has not yet reached that level of “black-and-white”ness, and therefore I feel it is not appropriate to be so aggressive about it yet.