If you want to enable the option to lock the target with the weapons, go in the configuration Options> Setup Controls> Configuring your Keyboard + Mouse, you will notice that it not possible to lock the target automatically with the click Right. We must aim manually.
If you still want to enable auto aiming with the right click, change the configuration and set it JOYPAD.
Surprise, it works! You can aim with the mouse buttons (but this will disable the (move camera) options).