Japan is working with the US to develop its own ballistic missile defenses, including one that can defeat incoming ICBMs.  The People’s Republic of China doesn’t like that.

Addressing a monthly press briefing at China’s Defense Ministry recently, spokesman Ren Guoqiang said Japan’s development of advanced radar systems designed to counteract incoming ballistic missiles would have a negative impact on strategic stability and damage trust between nations in the region.

Because a sound defense is a destabilizing threat to peace.  Because every nation being able to defend itself means no one can trust anyone—there’s no offensive threat with which to force “trust.”

Sure.

Never mind that, in addition to the PRC’s rapid development of its own nuclear offensive capabilities, including mobile ICBM systems and tunnel systems in which to secrete them; the PRC’s aggressions against Japanese islands in the East China Sea; and the PRC’s active occupation of the South China Sea and other nations’ islands within it, the PRC has been actively supporting (successfully) northern Korea’s drive to develop its own nuclear weapons and (nearing success) northern Korea’s drive to develop missile systems—including intercontinental-capable missiles—with which to deliver those nuclear warheads.

No, the only thing being destabilized is the PRC’s ability to threaten, to intimidate, other nations.