If anyone can deface your site at will, and it takes your manual intervention to fix it, you won't be able to just "set it and forget it" as you will be constantly babysitting your website.

Find a way to limit the damage one can do to the site by localizing changes to a randomized URL or something, because giving anyone on the internet access to your main demo is quite dangerous.

> do you really think I would put such nonsense on my own site

Well apparently you allow anyone to have access to what's shown there, so it seems you don't care what nonsense gets put on your own site.