There clearly were "sides" in this trial, in social media. It's not atypical at all when a trial has "overtones" relevant to society at large. Judges should not have a side other than justice, nor should refs, but the people assessing their conduct will claim they had a side. As for vigilantes, I think the term inherently implies a side of some sort.
Some of my liberal friends posted they were leaving the country as a result of this verdict. They won't of course, but they posted that, and other things, showing they clearly voiced a side. Some of their information that formed said "side" was factually incorrect of course.