If I had to choose the most insulting sentence currently available in the English language, it would likely be the following:
Those people are mistaken, for reasons I explained in a series of tweets.The source is here. For more immediate context, it's in reference to people who are in favor of the Oxford comma. The referenced Twitter arguments are of the usual Twitter caliber: glib, poorly organized, and myopic. The source organization, Poynter, is intimately concerned with journalism so I can forgive their editor's concern over generally trivial grammatical squabbles. I have more difficulty with the general concept of "you're wrong because of arguments I've previously made in the worst possible format."