There's been to many proofs that Chinese 'students' and 'researches' are actually well-organized spy circles, controlled from outside, both stealing every technology related stuff they can, and disseminating propaganda in the U.S. under direct supervision from China. They are not say like Russian or Indian students who try to adapt, blend into the ecosystem, and make it there. They are instruments in their State's hands. It's just a normal self-defense.