Totally agree with you
Hold on when did he follow his brother around ? Like stalk ?
He went to his company and waited outside to see whether his assumption about a girl being around his brother is correct, he hid behind trees or whatever and then he saw the female colleague being friendly with uke and assumed she is his girlfriend and when uke went back home he started questioning him. If you go back a few chapters you will see the uke looks around cause he feels like someone is watching him. I don't call this overprotectiveness but creepy.
I don't care whether he is homophobic. Shit is shit. Not only he made disgusting comments about homosexuality in the past but he treats his older brother like trash. What makes him think he has the right to constantly and rudely question him, make assumptions, follow him around, eavesdrop his conversation, and put him in a tight spot nonstop? Dude calm your balls down, your big bro basically raised you and all you did was making sure to push him in a corner where he had to hide his sexuality from his only family member for years. So yes, fuck the little bro 凸(￣皿￣)凸