The Summary of the siolution:
(I too wanted to disconnect facebook from Airbnb for whatever reason)
I followed 2 of the suggestions mentioned/
Step 1:
1. At the top right click on your Picture / Account.
2. Select "Profile"
3. Select "Trust and Verification"
4. Next to the Facebook option, click "Disconnect".
Step 2:
1. Log out.
2. Log in and select 'log in by email'.
3. Click forget password and enter email (the one you use for facebook = same as you use for Airbnb)
4. Follow steps of password reset.
Now you have succesfully disconnected facebook from Airbnb.