Sorry this guest has done this to you!..
some just dont get it is your home and not a 24/7 business. people dont get the concept of airbnb totally.
Try really really hard to be amenable, show them around and do your best.
if you cancel you will get penalized and the hassle of getting it sorted.
After they have left write in their review exactly what happened (facts) put thumps down to recommend them also.
You just never know they might be the best guest you have ever had bar this thoughtless act.
This is just my advice..
If you are too upset or cross about it then you must do what you feel best, as you wont manage to host as you would wish to.
Good luck, id be miffed also for sure.
mala