I think Trump would be better comparing it to how we use law enforcement to identify and run stings on pedophiles who try to recruit children on the Internet for sexual purposes. In this same manner, we should put our best people to identify and track down terrorists by USING the Internet, not shutting it down. I don’t think Trump really intends to “shut down” parts of the Internet.
Terrorist sites have been taken down before. Better yet would be hacking into the site the video of the ISIS guy yakking and then getting hit by a missile.