NOTE: This was written in the year 2162
1. We live in a society blessed with having the technology to build robots capable of interacting with humans and evoking, albeit artificial, emotions. They have a function. And that function is not to be your sex slave. That's first and foremost. Plus, there is no need for the robot to fill that role since Congress passed the "Everybody Is Permitted One Sex Slave" bill in 2156. Let's not get greedy.
2. Sex was not your robot's original purpose. Most likely when you acquired your robot, be it the standard KL39 available at Target or one you assembled from scratch, you did not intend to one day have sex with it. As you know, the "Domesticated Robot Boom" of 2140 was a direct response to what was known as the "Unironic Jetsons Drought" of 2138, which was of course, the natural result of the "Unironic Jetsons Boom" of 2130.
3. Your robot is designed to compact large metal objects into pocket-sized waste. Think about what it can do to your jambone.*
4. When it comes to personality, all robots come with a blank slate. You filled in the gaps. Since the great "Celebrate Your Soul Before It's Stolen by General Zooooog" movement of 2104, all humans have forced their personality, likes, dislikes, fears, joys, anxieties, jimpans, and idroots into everything they encounter. What does this mean? That your robot has taken on your personality. Having sexual relations with your domesticated robot would be like having sex with yourself. This of course, violates "No Unnatural Sexual Thoughts" ordinance of 2098, which is punishable by death.
5. Since your robot has taken on the personality of someone well aware of society's laws, it will be keenly aware of the illegality of your sexual advances and will fight off any attempts you have at making love to it. Since you likely configured it with the Hotwired History™ data chip, it knows of, and is greatly troubled by, the "You Can't Rape Robots" bill that was passed in 2118.
6. On the off-chance that your robot enjoys the sex, it will celebrate its orgasm by ripping your arms out of their sockets and murdering your family.
*Assuming you underwent the government ordered Jambone/Penis switcharoo in 2152.