Why hang glider dont over pitch when inrease AoA?
The short answer is that the wing itself is designed to have sufficient excess pitch stability such that the glider-pilot system is still stable in pitch when the pilot's weight is shifted somewhat aft.  If the pilot's weight is shifted sufficiently far aft, however, a stall may occur. The glider might not recover into stable flight if the control bar is kept pushed that far forward, i.e. if the pilot's weight is kept shifted that far aft.
It is normal to trim a hang glider to fly in wings-level flight at an airspeed near the minimum sink rate, not too far above stall speed, when the pilot is exerting no pressure on the control bar.  It would be normal for the glider to stall if the pilot extends his arms as far forward as he can reach, in wings-level flight.  A hang glider pilot would not necessarily expect to see benign flight characteristics if he keeps the bar pushed forward as far as his arms can reach, in wings-level flight.