This problem is not new. On a $1500 cad stay they charged me in CAD and performed the conversion. I asked through multiple emails to opt out of the Dynamic Currency Conversion, as is my right, I believe as a consumer. They declined. I called and escalated the matter. Still declined.
Here's where it get's interesting though: I then tried to change my card later on for a different purpose. I was switching from Amex to Mastercard to fulfill spend requirements. They informed me over email that I would not be able to issue a chargeback for the DCC. I never had an intention of doing that, but now that they said it, I googled it, according to Visa/MC rules you can issue a chargeback for DCC. Airbnb seems to know about this and actively tries to dissuade you from doing it. I find this whole thing disgusting on AirBNB's part.