There is literally nothing in that scene to suggest anything sexual. He's sarcastically congratulating him on defending his city, because he managed to do it by pledging his bloodlines allegiance to Bwonsamdi. Bwonsamdi is taunting him and Rastakhan seems full of regret and remorse.
I don't see how you can find anything sexual in that at all. Its a scene highlighting how fucked Rastakhan and Talanji are.
It's getting comical now, your Bwonsamdi fetish.