That right there - where you call the homeland of a nation a "buffer region" - is the problem. China has the right to take care of its national security, sure. But not at the expense of the right to self-determination of other nations.
Regardless of all that, though, Dalai Lama coming to speak is not an "attack" on Chinese students.
Regardless of all that, though, Dalai Lama coming to speak is not an "attack" on Chinese students.