Why can't a robot love? Because they can't have sex?

[UglyBastard]

Is it possible to have a real relationship without sex? I know that some may argue that the primary biological function of human beings is reproduction, but I disagree that this is so important nowadays. Sterile women can't bear children, sterile men can't inseminate eggs with their sperm. So these people couldn't have a real relationship?
If we can take sex out of the equation, then why couldn't the relationship between humans and robots be real? I can talk to an AI, I can represent it through an avatar in the virtual world, I can put that AI inside a robot when that's possible, etc. The only thing we might not be able to do is have sex, at least not initially.
What about love? Can you prove that your girlfriend loves you? Can she prove it to you? How do you know that love really exists? How can you question that an AI is capable of love if you can't even prove that the love your mum feels for you is real?