I dunno, all this Berserker armor shit is doing both at the same time, so it's kind of nifty like that.
Also, someone hit it before. Guts overhears Griffith and Charlotte on the ball night where she says he has so many friends and he's like, "Nah, they're not friends, they're followers. A friend would be my equal, he would have his own dream to follow, even if it meant setting himself against me." So Guts, seeing he was never really Griffith's "equal" or "friend" decides to find his own way. Griffith, wants none of this, so he tries to stop him and gets HANDLED. Guts leaving makes Griffith realize he isn't totally in control and that his definition he just gave is completely wrong. And if it is, well...he's wrong about a lot of stuff. And he can't face up to that, especially now that he doesn't have the friend he sort of took for granted.
As for the rape, I don't see why it's so out of character. He JUST turned into a Godhand. They kinda do what they want, often dickishly, and with a surprising amount of rape. Everyone describing Griffith as cold and etc. are describing newborn baby human-world Griffith, not Godhand Femto, who we saw very little of. And when we did, rape really wasn't out of character for him if it was used against someone who basically showed him that he wasn't always in control or right.