I think Japan is overreacting as well, but Japan and I may see this differently because of cultural differences. Despite the custom to drink after work, it may be unacceptable to get so drunk that you expose yourself in public. Maybe Japan thinks public exposure is a great misdeed. I don't really know.
I thought Japan overreacted when the Koda Kumi incident happened, and I thought that what she said wasn't that big of a deal. But I guess due to cultural differences, Japan saw it differently.
I'm a bit ambivalent toward this incident. It's kinda amusing, but it's also kinda sad to see that Tsuyoshi basically tarnished his career with this one mistake. In my opinion, he doesn't deserve all the scorn and criticism he's getting at the moment. Sure, he's an idol and therefore should behave well; I agree that his behavior wasn't right. But it's nothing worth getting so angry about.
I hope Japan will soon forgive him and that they won't hold this incident against him for too long.