ジャップの司法に期待するとか無理

まさにこの通りなんだよ
一部のお前らと違って矛先がわかってるわ

https://www.reddit.com/r/Hololive/comments/lhnqtw/screenshot_of_message_from_jpbros_a_reminder_how/
Real life idol companies can't do anything about this situation either.
When Korea's JYP entertainment's idol group Twice showed a Taiwanese flag in one of their music videos they were forced to apologize by antis and take a break.
And they are way bigger than Cover and Korea actually has anti-doxxing and anti-harrassment laws unlike Japan, but none of that matters.
Their group still has bots and antis spamming them and they don't even live stream.
I don't know what you expect their management to do but at this point only YouTube can fix the spam problem because ultimately it's YouTube's platform.

--

Need to be said that this is an automated bots attack.
The only thing could filter this out is an AI, which Youtube did and it still not in perfect state.
As theres no kind of algorithm using pattern recognition would handle all of this, all they do is just simply change the message content and it would bypass any filter put within the stream.
This isn't something Cover could do.