This is a joke - right? Do you have other rules - like no blacks, Asians or other ethnic groups?
If it's not a joke then you need to look else where for your business - AirBnB is to help people meet up and exchange cultures, thoughts, conversations - very unlikely you will get any bookings if you put something so insulting in your profile. But go ahead and check what happens.
As you are aware, in the UK you are now deemed to be running a business as you get a tax break on the first £1000 of earning from sites such as AirBnB, so thankfully you will also be breaking anti-discrimmination laws.
As for it being a matter of conscience - I think you will find it's education that is the root of your issue, not conscience.