Who said anything about him being an equal if he was allowed to be used sexually? Adam certainly didn't. He doesn't think using H-13 in this manner is going to make the android any less obedient. If anything, the way Adam acts when he's allowed to release his tension is only going to make H-13 feel more inferior.

He watches with a grin as H-13 gets more and more worked up, acting so much like Kotetsu would. He must truly be feeling something, even if it can't truly be anything like human pleasure.

His grin fades as he lets out a slight growl, digging his nails a little forcefully into H-13's hip.

"What would give me pleasure is having you follow my orders. I have no opinions on what will make me feel better."

What matters is that he's in control, which he doesn't doubt he is.