True it is a double standard, but I have a hypocritical way of making it seem fair:
My woman consents to the threesome with another woman, therefore, she has no reason to be angered that I have sex with that woman in her presence.
I do not consent to a threesome with another male because I do not want that form of contact with another male... furthermore, I feel I have to be the only one to satisfy my woman.
And my woman alone with another man? That sounds like cheating... i.e. she will be IMMEDIATELY dumped.