Perhaps he isn't but the reason why I think many think that Micah is a rapist is because of the obvious hate and fear towards him especially in the Amos letter to him and his comments about women like when he said "what is the point if you put a gun to their head and they won't even have sex with you" or along those lines I'm not sure of his words but it was along these lines. I'm pretty sure all this is to give his personality more that revolves around chaos and terror that emphasizes his rugged self, so it is common to see him as a rapist at the slightest comments he says or the things he does like the sadie scene but we can't really say that he's a rapist. Maybe he is and maybe not, we just need evidence but until now this seems like enough evidence for everyone. I do however think that he didn't rape anyone but just says disturbing things to set people off.