If his posts are spam or he is self voting for large amounts, then sure it's abuse. On the other hand, if they are legitimate posts, why should he not be able to make them? That's what this platform is for and presumably at least part of the reason he is interested in it. Also, I think being a witness, particularly a top 20 witness, is a lot more work than a one time server set up. Plus, there are monthly costs associated with running a server. I don't doubt that top witnesses make a profit but it isn't ALL profit. Downvoting for disagreement with rewards is the way to go. Leave a polite comment explaining that along with your downvote and I don't think he would revenge downvote but then I could be wrong.
How about this post? Is it worth $5.38 (which is what it is as I leave this comment)? If I downvoted it (for maybe a whopping 1 cent reduction) and left a comment that said. "Nothing wrong with the post but I just don't think it is worth $5+...downvoted for disagreement with rewards." would you then start downvoting my posts for revenge? Not all people are rational of course...
The answer is yes. He would retaliate. It's a proven fact about this leech posting this dumb question.