Okay ! So ! HJ was fighting demons during that scene (he is still fighting demons SH won't let this man breathe) but yes, during that scene was the first time HJ was confronted with the stark difference between his rational mind as a father and his baser instincts, because HJ is just a man. SH already broke his brain the first time they shared a bed and SH took advantage of the situation, so HJ already perceives SH as more than just his child at this point whether he likes it or not (he does NOT like it)—he’s had to confront the fact that SH is a grown man and hence a sexual being.

So once you think something, you can't unthink it and once you feel something, you can't unfeel it. As far as lust/arousal is concerned, you can't control whether you feel it or not—its an impulse, an instinct—but you can control how you react to it. HJ has been doing his best not to lose his grip on self-control and not to indulge that impulse (his anger as well but that's another story) and he flip flops between being good at doing so and bad, depending on just how close to the edge he is.

During that scene, the visual and tactile stimuli of having SH in that position bent over in front of him and bared to him, was too much. Again, at this point HJ has already been forced to see SH as more than just his son, so despite it not being an active choice, or actively thinking about it in a sexual way—he is aroused by the sight and sensation before he gets into the doling out punishment part which takes him out of it.

As far as causing SH physical pain is concerned, HJ is again stuck between his role as father and man. Because as a father, he absolutely abhors the idea of hurting SH but as the man who is struggling and confused and hurt by SH’s actions, he does want to hurt SH to punish him for starting all of this and ruining the relationship they used to have with one another—something HJ treasured deeply. HJ feels just as satisfied after hurting SH as he feels horrible about it and that satisfaction comes in different forms. It's simple in the sense that it's a release of tension, the anger and everything else he suppresses. It's feeling good about hurting SH because SH doesn't seem to care about how his actions are hurting HJ—if he did then he'd stop pushing for more, right ? (Sh has his reasons for not doing so.) The pleasure/satisfaction hj takes in inflicting pain is obviously sadistic and mostly in a non sexual sense. The intensity of HJ's sadism isn't very strong during this scene, but grows throughout the fic hand in hand with his frustration and anger—even if he doesn't act on it, trust me it's there. HJ wants to hurt sh and the knowledge makes him very guilty which in turn influences how much he gives in to sh to make up for it.

Anyway, HJ's arousal in that scene was just more incentive to go through with punishing SH the way he did because the fact that lust is no longer something that lies outside the boundaries of his and SH’s relationship pisses him off A LOT because it wouldn't be that way if it weren't for SH forcing it upon him. HJ hates not feeling in control and as time passes, he feels like he's losing more and more of it and it's frustrating him as much as it's worrying him because SH is the one who's going to have to deal with what becomes of him if he loses it completely.

There is a part of HJ, the rational and more dominant part, that is trying its damnedest to maintain boundaries between himself and SH but then there's the part of him that is attracted to SH in the simplest and most basic way he could be; the same way any man would be to someone they think is beautiful.

HJ giving in is of course its own convoluted matter that involves far more than simple lust. There's just a lot going on with the both of them. I honestly don't know where to start to touch on all the points and reasonings behind the way they respond to things and the decisions they make. It's all so twisted and complex and talking about one thing is difficult because there are so many other factors it relates to that I don't feel like I'm doing an explanation justice and end up rambling trying to make sense of it but it's never enough.

Anyway, isn't it just great to be human and be able to hold onto so many contradictions all at once…HJ is fighting for his life fr.