I disagree that protecting our editors from harassment must come at a cost to the encyclopedia's content. We remove links, sources, and participants day and night in order to improve it. Let me compare this to three other situations: spam, fan forums, and lawsuits.
I remove dozens of commercial spam links to every week. Arguably, those many of those links could provide some benefit to readers. An article on recreational vehicles may, in some folks mind, be improved by providing links to stores selling RV accessories or used RVs. Yet we've decided that commercial links are inappropriate because they would overwhelm the articles and because they do not provide any actual content. Their harm outweighs their good. Likewise, links to external harassment that drives away valuable editors also cause more harm than good.
Fan forums and blogs are routinely deleted (with very few exceptions) because they do not provide reliable information for our readers whether used as a source or for further reading. Forums and blogs that engage in active harassment of editors of a reference work are even less reliable as sources for that reference work.
Finally, we do not allow people who have said they are planning to sue the WMF to edit Wikipedia because they have an unavoidable conflict of interest. So does someone using harassment. The person in charge of a self-published site that is harassing Wikipedia editors is trying to affect the project in inappropriate ways. We can't stop them from doing so but we should not view them as neutral or even reliable sources while they pursue their agenda against the project and its volunteers.
In all three of these cases restricting inappropriate links, sources, and participation improves the encyclopedia instead of harming it.
W.