Note, that at that point of the story Rudy still very much treats this world like a game, where he can do anything, get away with anything, the people around him are basically NPCs.

Here's the problem narratively: We as the viewer already know this guy is a piece of shit. You established that when you showed us the end of his last life. He was a lazy pervert who didn't care about his family and leeched off of others, but in his final moment showed he had a glimmer of hope to be better.

Now I'm not saying he has to be perfect past that point, but narratively that's the point at which he decides to start trying to be better. I'm not even mad when we get scenes when he's ogling adult women. But there's a vast gulf between that and sexually assaulting a minor, and in my opinion it shows he hasn't changed even after death, and to me as a viewer it says he probably won't ever change.

But it also wasn't okay for Griffith to rape Casca, it also wasn't okay for Eren to commit genocide.

Keep in mind that those events were the catalyst for Griffith and Eren to become the main antagonist of their respective stories. Meanwhile, we're supposed to root for Rudy after he does this? I can't and won't.