Firstly, I suggest you apply to be admin for that section here:
I was certain we had a Japanese admin, but he must have left/retired.
If you do choose to become admin, general guidance and rules will be sent to you and you can moderate the Japanese section.
It's best we have a native speaker.
Secondly, we don't ban users just like that without giving them a warning first. As the Japanese section doesn't have an admin at the moment, he's probably as upset as you are about the machine translations, just doesn't/can't express himself amicably.
The Japanese section doesn't seem that busy with the amount of uploads coming in, so can't imagine it would be a difficult job for you, as long as you have an hour to spare and to check it every couple of days.
Do consider joining and helping the community.
PS: Can't find a user by that name, must have deleted his account. User search is case-sensitive.