X11 Authentication Error when run as a Docker container

I'm trying to run an application from a Docker container which is supposed to open a GUI widow (a video stream in my case). The Docker container is run on a Raspberry Pi and I SSH into the Pi from my Mac and then I issue the Docker run command. I have one problem here:

When I run the whole thing as follows, it works flawlessly:

1. I run the command as:

docker run -it --net=host --device=/dev/vcsm --device=/dev/vchiq -e DISPLAY -v /tmp/.X11-unix joesan/motion_detector bash

2. From the bash, that opens up after issuing the Docker run command, I install xauth

   root@cctv:/raspi_motion_detection/project# apt-get install xauth

3. I then add the Xauth cookie using Xauth add

4. I then run my Python program which shows the GUI window with the video stream

So far so good. But, every time I don't want to be doing these steps all over again. So I wrote a small script to do this as below:

HOST=cctv

DISPLAY_NUMBER=$(echo $DISPLAY | cut -d. -f1 | cut -d: -f2)
echo $DISPLAY_NUMBER

# Extract auth cookie
AUTH_COOKIE=$(xauth list | grep "^$(hostname)/unix:${DISPLAY_NUMBER} " | awk '{print $3}')

# Add the xauth cookie to xauth
xauth add ${HOHOSTSTNAME}/unix:${DISPLAY_NUMBER} MIT-MAGIC-COOKIE-1 ${AUTH_COOKIE}

# Launch the container
docker run -it --net=host --device=/dev/vcsm --device=/dev/vchiq -e DISPLAY -v /tmp/.X11-unix  joesan/motion_detector

But this time it fails with the error:

X11 connection rejected because of wrong authentication.
Unable to init server: Could not connect: Connection refused

I then tried to run the above script as a sudo user and I get the following:

xauth:  file /root/.Xauthority does not exist
xauth: (argv):1:  bad "add" command line
X11 connection rejected because of wrong authentication.
Unable to init server: Could not connect: Connection refused

Is there anything that I'm missing? Please help!