There's something about bad sex...it makes you feel awful, wretched, abnormal, confused, upset, insecure....Sex may be the most instinctual thing humans do anymore, and we all know when we feel the sex is bad, when it's good, and when it will do.
The father/son thing has been getting to me from the start, but then I pause to consider. This chapter, especially, told me that Teddy's had a rough time of it. Sex hasn't been satisfying for him and he feels he hasn't done a good or right job of satisfying others and Remus comes along and blows all his perceptions wide open. Teddy can feel good, he can give someone pleasure, even when he doesn't quite know what he's doing. It's an incredible gift and huge, sobbing relief to Teddy, I'm sure, which is why his reactions are so emotional, and Remus probably has no idea how many of Teddy's tensions and fears he's putting to rest each time they meet.
However, there is something to be said for having a safe environment for these things, a person and place in which you feel comfortable to explore, which is Remus' end of the argument. If parents could somehow give a safe and comfortable sexual learning environment to their children, I think many would. I think when Remus gets to really thinking about it, he realises that Teddy's sum total sexual experiences with his preferred gender have been rushed and full of fear, quick and probably rough, all a means to an end. It's sad, when you think about it, that Teddy's first time doing so many things was driven by anxiety rather than tenderness. So, Teddy's early sexual history is something I think Remus can imagine very well, and I think it's something he would fix for his child, if he could. It's a chance Teddy has given Remus by seeking his comfort and safety. Which is why I can keep reading.