This is an interesting decision and I applaud Troy for, as always, doing what's best for his users. He's a great example of the kind of person we need more of in the industry.
Unfortunately, I run into the same problem. I have no doubt people can (and probably do) use dumpmon for nefarious purposes. My take on the matter when I first made dumpmon was that this data was clearly already known to the bad guys. The goal of the Twitter bot was to give a sense of how prevalent these "mini-breaches" were, but also to give the good guys (like HIBP!) a feed they can use to help stop the problem. I've been fortunate that multiple services have been able to use the feed to respond to these types of credential dumps really quickly.
If anyone is interested in some of the stats behind dumpmon, here's a shameless plug to an article I wrote a couple of years ago on the matter: https://jordan-wright.com/blog/2015/05/26/two-years-of-at-du...
Happy to answer any questions!