You obviously don't know enough about Bitcoin to argue the way you did. If there is X hashing power and you need X/2 to control the network, then reducing X by

You obviously don't know enough about Bitcoin to argue the way you did. If there is X hashing power and you need X/2 to control the network, then reducing X by 50% means that you only need X*0,5/2 to control the network. The difficulty is only adapted every 2010 blocks which equals around 2 weeks but if you suddenly cut the hashing power in half, this will take up to around 4 weeks and slow the network down immensely.