From what I can tell, the YouTuber in question throws when they get matched with 'subpar' teammates, and also has said abusive stuff during videos and live streams. (Nintendo has even taken down one of their streams via copyright strike while they were live.)

There's been a few problematic YouTubers in the Japanese Splatoon community lately. I think they are the reason why Nintendo made this change to their copyright policy (so that Nintendo can issue a copyright strike if they step over the line). 🐦 original post

would you happen to know if this is a certain Tetra Dualies player?