If the user was banned from Discord for voilating Discord TOS I don't see why the burden should fall on server owners. It should be Discord's responsibility to enforce sitewide rules and take down hateful content.
From the article, the boycott is not particularly widespread.
> It's hard to measure how widespread the boycott is. While the hashtag #ADayOffTwitch is getting some traction on Twitter, there isn't much discussion of it on the popular Twitch subreddit r/livestreamfail as of this writing.