Period.
1. i don't think they were hosik's friends, in the raws hosik uses -yo when talking to them so it's likely that theyre his seniors and so far only samsik and jiwoon have been shown to be his friends. i don't know korean that well though so i might be wrong about this
2. i think sungyeon was calling them out for forcing hosik into being in the team for whatever it is they're doing. in chapter 41 hosik says that he didn't want to do it, and since theyre talking about him having to go to a meeting i think its safe to assume that they forced hosik to sign up to something. and then sungyeon says that he asked them exclude hosik from the team and he won't be called around anymore. and considering all 3 of them were in a pretty bad mood afterwards, i think thats what happened because if sungyeon told them off for hitting hoyeon then only the guy who actually hit him would be upset
i agree that sungyeon shouldn't be going around scolding everyone who does something wrong to hosik but hosik is unable to tell people his opinions firmly so in this case that was actually a rather nice thing to do, and also you can see hosik was grateful for that
Like I understand what happened with them accidently hitting the baby and being forceful about hanging out with him. But if they are their friends I find that completely reasonable, and I think it honestly had nothing to do with sunbae. Like legit what you valling them out for, it was a honest mistake, he apologised a d we see that he did feel bad about it. I just feel like he's waaaaay too controling of Hosik's life, he needs to chill. And Hosik needs to learn that although he's still young he has a kid and needs to grow up and start handling his situations by himself. And I know that he's married and they must share their problems, and if you see your loved one in a hurdle you are going to help. But thats it, you help them, is not you getting into the situation and fixing it while the other person is hidding away. Hosik needs to start pitting a strong face and stop all this bulshit of "Im too sensitive, you deal with it". He has a kid even if he wasn't ready for it, he has it and just has to learn to deal with the hard parts of that.