As annoying as he was, he makes a good point.
Is Aoba really going to just let it rest at "looking after their siblings"?
Aoba needs to get a move on. His much-less-objectionable prettyboy friend intimated it was well--he needs to get his act together and stop acting in half-measures and noncommittal "overly-conscious" ways.
If even an asshole like the senpai can simultaneously say "okay maybe you were right" and accurately call out his temerity?
That should be a wake-up call.