Would you mind teenagers and Twenty-somethings learning about sex by fucking a sex-robot because it's more convenient than hitting on somebody?
A dildo is a sex-toy and it is clearly discernable as such. It gives you an orgasm but it doesn't look like a human, it has no affection for you and you have no affection for it.
However, a sex-robot would have a human form and it would simulate affection for you. It's not a question of if but of when humans apply anthropomorphism to this humanoid and start treating it as a human.
For example: People treat their pets like children.
For example: People base their judgement of other people/things on looks, not on internal qualities. People regard something as "cute" if the phenotypical representation triggers instincts normally triggered by human babies.
I am talking about the cultural implications when "people" and sex-toys become psychologically one and the same.
If people make an emotional connection to the thing that comforts them and makes them happy, then they treat their sex-toy emotionally like a human.
Imagine what it would be like, growing up in a world where you are free to have the choice:
1. Get a robot-girlfriend/boyfriend who is always there for you and does everything you want, no questions asked.
2. Approaching a stranger, with a risk of failure. Talking to said stranger and getting to know said stranger, with a risk of rejection. Establishing an emotional connection to said stranger over the course of weeks (statistically, the first sex happens between the 9th and 18th date), with a risk of rejection. And then having sex with him.
What would be the emotional difference between them? Why would you treat one different than the other? Human relationships are more complicated, so they would be less desireable than today, because there is an easy alternative. This would mean your moral compass wouldn't automatically regard human relationships as "nomal". "Normal" is as people do. And it would be normal for people to fuck things that do as they are told.