Then it is perhaps your choice of morals I have a problem with.
A set of principles that places the activities of one set of consenting adults over that of another for the sake of tradition alone.
I despise and cast out the clerical snoop and the holy peeping Tom.
If you define the marriage of members of two different but sentient consenting sapient beings as bestial then I defy that too.
Some of my best friends are alien half breeds and I view with contempt any cad who dares call them beasts.
How on Earth do you get through your day by calling two siblings living together incest? It's just sound economics and frugal living.
It's only incest if the have sex with each other and not everyone who is married has sex with each other (in my experience hardly any of them do).
But no... it's all sex with you isn't it?
Sex, sex, sex, sex, sex!
*can I have your telephone number?*