I feel like Hiroharu is that 1 meme that's like "when someone is so bitter it inspires you to be kinder"
He saw a glimmer of hope in a broken and used person and didn't give up on them when others would have. Of course it's not your job to be your partners therapist, but helping them come to terms with their feelings by simply loving them and sharing your opinions and letting them make their own decision is a good way to go about it.
I also liked that last scene with him and Goh. He didn't need to say anything mean or snarky to him because he already had the higher ground. He already won the battle, what would be the point of starting a needless fight. Killing with kindness works just fine.
And for those saying Goh needed to be put in jail. Ye he did, in an ideal and just system. Let's be real, if this happened irl nothing would have been done about it unfortunately and he would have just become more agrivated because you tried to put him in jail. Sometimes it's more dangerous to try and sue someone and fail than just letting them go and never seeing them again. That being said, I hope he finds happiness in his next relationship that lasts a long long time, and then gets stabbed in his sleep after his S.O confesses to cheating on him