I hate to play devils advocate here- but is it possible he was just being an idiot?
Maybe he was trying to help out and clean the oven for you so the house was clean- and thought he'd kill two birds with one stone by throwing the dutch oven in there?
I ask because as you know I own a cleaning business- people do all kinds of dumb things like that, and destroy their houses simply because they don't know any better.
I had one guy moving out- he sprayed oven cleaner in the oven then turned the self cleaning on
He thought he was doing good.....
Xoxo
Someone else used a heavy duty lime remover on their hardwood to try and clean it....
The list goes on