So no one said that he would or even may turn off the internet, but that he may use legalize and his emergency presidential powers, if elected, to do something crazy. The person talking about it was spitballing and included turning the internet off as a example of something crazy that he might do.

Edit: He indeed talked about geoblocking countries with groups like ISIS operating within them. At least that is what I assume he meant with his word salad. This is from post below mine. Still not turning off internet.