Instead of giving in to his wishes, I have turned off the light and tried to sleep. He makes the same vocal sounds even if he is on the bed, and will often go further and swat me with one of his front paws until I relent. The result of all these points is one clear argument. With only a minimal amount of encouragement, the dog is actively seeking sex. To argue that it is perfectly acceptable to encourage your dog to sit on command but not acceptable to offer your dog pleasure in the form of masturbation or some form of penetrative sex is to fall into the trap of 'moral outrage'.
Morality engendered by religion or upbringing is a hard force to argue against.
This form of denial is a particular problem when it comes to sexual morality. Popular sexual mores have been put on the pedestal of popular morality for such a long time that they have gained an almost teflon-like resistance to stones cast at the irregularities in the logic of their proponents. If you try to argue them down, you end up hitting the brick wall of social acceptability. This problem makes it very difficult to claim validity for any of the arguments presented here. Animals can consent to sex with a human partner.