His son is also a teenager with raging hormones, insecurities, and in the middle of the phases towards self discovery. The father did that BECAUSE he understood his son's feelings so well. He even had that line of "he really is exactly like me" http://www.mangago.zone/read-manga/katakoi_kazoku/mf/1fc97123f9fff721fbaed358347380d1_chapter-6/pg-16/ . It's not as though any act in the situation is a perfect solution. All in all, I don't have the heart to call him a bad guy. Sure he's the story's technical antagonist, but the story will develop and the characters will change for a better ending.
On the contrary, I don't think he understands his son's feelings at all. All he did was call him a brat and scream at his face, basically telling him he's good for nothing. He didn't talk to Kazoumi further about his feelings and what he has been going through, why he's no longer doing Kendo, etc. He also doesn't have a conversation with Shinobu about his feelings and thinks nothing of the fact that he says he wants to see Kazoumi. Then he forcibly separates Shinobu and Kazoumi (as if Shinobu isn't an adult with his own free will) and makes sexual advances on Shinobu, his brother who also is married, offering to have sex with him in place of Kazoumi.
Also on the page you linked, 'Nii-san' says "It's in Kazoumi's best interest to realize that he can't do anything by himself". That further indicates that he doesn't understand, thinks his son is worthless and feels he can't / should not have any independence or free will.
So yea, I solidify my opinion that 'Nii-san' is a piece of shit father and piece of shit brother.
So you're just going to hate on story drama? Yeah that would be the point of it tho
After reading chapter 6,......Nii-san is a piece of s**t -.-
Doesn't consider his Son's feelings AT ALL. And then goes and puts Shinobu in a really difficult position....nice brother /sarcasm