@weebycunt : I already explained why he didn't report it.
And there was no need to paint him as a "nice guy". She ALREADY wanted to ride his meat-stick. This was just an event to give the impression that she had tried for other clubs, and to demonstrate that the other clubs were found lacking so as to shoehorn her into his little ancient research club with the pseudo-kuudere.
Also you call it basic human decency, but be real here... most people wouldn't step in if they were alone, or at most would only step halfway in. There is no "basic human decency" because basic humans aren't decent. Regardless though, there was no tension nor drama because the guy was OP from the start and there was absolutely no danger to him to step in and engage in PG-13 level violence.
See... there ARE things wrong with this scene and this manga in general... but I reckon you've completely misinterpreted what exactly is wrong about them.
take goblin slayer for example, rapist goblins were kinda new and served purpose to the plot to show how fucked up goblins can be
Kekeke.... seriously?
Do you think Goblin Slayer invented rape-goblins or something? Hate to break it to you, but this sort of stuff stems back at least as far as Berserk's Fantasia arc if you're only counting mainstream fiction... As far as hentai goes, it is such an ancient trope that it is stranger for goblins (and orcs, obviously) not to immediately start raping anything remotely humanoid with female parts. It hasn't been new for decades... and frankly Goblin Slayer is still a recent fad.