First, it's the door LEADING to the gas chamber. Second, this is a reconstruction, the S.S. dynamited the originals when they fled.
Look, we get it, the Nazis sucked all the fun out of antisemitism. The Holocaust was the logical end result of your way of thinking, and you can't reconcile this with the concept of wanting to be a good person. So you need the Final Solution to be fake in order to keep from dealing with the idea that deep down you'd sign up to wear a Swastika and do the exact same things.
My advice is to embrace the evil, and bask in the glory of the S.S. If you can't then you need to rethink your life.