I think cheetah bot is a valuable service and I hope to see it continue. I think the message from the bot needs refining though. I'd suggest saying as little as possible in the message and not making even the slightest mention of the word plagiarism or suggesting wrong doing. Say you are a bot, display the link to matched content and that's it. You might consider linking to an info page about your bot, how it works and how to get on or off your white/black lists etc. Just keep the comment short, simple, and positive.

In the future there may be many alternative ways of handling the copy/paste issue, such as a dedicated site for such identification or steemit.com themselves displaying helpful information like "related articles" or "web search similarity stats" ... or something.. I don't know. : )