It is an interesting evolution of internet era tribalism. On other internet communities like reddit and twitter, when two people disagree on one subject they color in their mental image of each other with more disagreements, to presume they would disagree on everything. This way they can make the other person the "enemy."
On an anonymous message board no one has a recognizable identity. They try to color in pictures that don't exist and the colors go everywhere. So it fosters the paranoia that anyone could be an enemy and that they're surrounded by enemies.