MouseLook Disable function

I am trying to disable the MouseLook when the left mouse button is clicked. However the code I have put in does not do that and I am not quite sure why. Any help would be greatly appreciated. Here is the code:`

class MouseLook : MonoBehaviour {

 public enum RotationAxes { MouseXAndY = 0, MouseX = 1, MouseY = 2 }
 public RotationAxes axes = RotationAxes.MouseXAndY;
 public float sensitivityX = 15F;
 public float sensitivityY = 15F;

 public float minimumX = -360F;
 public float maximumX = 360F;

 public float minimumY = -60F;
 public float maximumY = 60F;

 float rotationY = 0F;

 void Update ()
 {

     if (Input.GetMouseButtonDown (0) = false) {



     if (axes == RotationAxes.MouseXAndY)
     {
         float rotationX = transform.localEulerAngles.y + Input.GetAxis("Mouse X") * sensitivityX;
         
         rotationY += Input.GetAxis("Mouse Y") * sensitivityY;
         rotationY = Mathf.Clamp (rotationY, minimumY, maximumY);
         
         transform.localEulerAngles = new Vector3(-rotationY, rotationX, 0);
     }
     else if (axes == RotationAxes.MouseX)
     {
         transform.Rotate(0, Input.GetAxis("Mouse X") * sensitivityX, 0);
     }
     else
     {
         rotationY += Input.GetAxis("Mouse Y") * sensitivityY;
         rotationY = Mathf.Clamp (rotationY, minimumY, maximumY);
         
         transform.localEulerAngles = new Vector3(-rotationY, transform.localEulerAngles.y, 0);
     }
     }else if (Input.GetMouseButtonDown (0) = true) {

     }
 }
 
 void Start ()
 {
     // Make the rigid body not change rotation
     if (GetComponent<Rigidbody>())
         GetComponent<Rigidbody>().freezeRotation = true;
 }

} `