We have a term for the type of speech that spurs stochastic terrorism already. It's blood libel. https://en.wikipedia.org/wiki/Blood_libel

If you spread lies about a group that demonizes them you put members of that group at risk.

For instance, if I started a viral rumor that white male computer programmers all keep sex slaves under their houses and enough people believed it a lot of the people on this website would suddenly be living much more difficult and dangerous lives as lots of strangers would assume that they were evil monsters who needed to be put down for the sake of children without even getting to know them. The murder rate against white male computer programmers might even rise noticeably as they became a target for random violence by people who wanted to do a "good deed" on their way out of this life.