Of course there's no off button. There's no off button to who Bruce is and Bruce is Batman.

Those hands are gentle as they slide over the curves and dips of muscle and bone, and the smile on his face isn't so much lustful as it is... happy. Being with Bruce, getting to do things like this, makes him happy. The lust is just a part of that, shown by how reverent those fingers are.

"Lay down?" because he did mean it when he offered to give him a backrub.