"What, if anything, can be done...other than make my tree Private?"
Making your tree private (an option which I use), you will almost certainly neutralize your most effective tool for correcting genealogical misinformation. If you elect to keep your tree "private", create a smaller tree containing your strongly sourced data and make it public. It will, more than likely, eventually prevail over the misinformation.
That being said, if the thrust of your point is to advocate for some type of "intervention" when tree owners are unresponsive to making corrections, other than alerting ACOM to some legitimate copyright violation, you're tilting at windmills here. The right to be wrong is integral to freedom of expression. While you're free to curse the darkness, it's better to light a candle.