It doesn't mean "oh My god rape sometimes is necessary!!". It's just a part of the plot that's needed to tell the story. Yes, the story could've been something else entirely. The rape scene could've not been necessary. But this is the story. Sometimes bad things happen in stories and some of them may seem forced, but not in this case. The rape scene was not a fetish nor suffering without point, it actually is vital to understand the story. You could've not told the story without it. I think we shouldn't ban certain things from stories just cause they are bad. Stories should be different and sometimes sad and frustrating. The point is that stories tell stories. Wouldn't make sense to just tell good stories without death or suffering.
I do think some rape scenes are completely unnecessary in yaoi cause they tend to romanticize it or just add it out of fetish of the author or god knows why. But that doesn't happen here. Rape here is much more than just rape without meaning in a story. I do think some people may just not want to read rape scenes at all and that's fine. Just understand that some stories involve it cause that's just life. It exists and sometimes you tell stories that involve suffering. Is rape bad? Yes, of course. Is this story saying the opposite? Not at all.
I think that's what they meant with "rape scene was necessary".

Guys please the rape scene wasn’t unnecessary I would agree with y'all usually but it’s actually so important to the plot the whole point of that scene was Dante’s father PURPOSELY putting them in that position to test his son’s loyalty and simultaneously hurt Gino. The scene continued to show how ruthless his is and how little he cares about other people bc he KNOWS they loved each other. The rape scene WAS necessary and PLOT IMPORTANT! It’s supposed to make you feel uncomfortable and sad, good stories make you feel emotions guys!! And Dante was also PURPOSEFULLY trying to make Gino hate him!!! He was doing EVERYTHING he could to get him to hate him guys please the story is actually so good please use critical thinking not all yaoi is noncon slop just bc it has rape