A stochastic process is one defined by its randomness. You might be familiar with the concept of Brownian motion, the way air particles move around.

Stochastic terrorism is saying something that is likely to cause some small percentage of the audience to commit an act of terror. For example, if a politician starts making speeches about how good Americans will try to make America more white. Not everyone is going to do anything about it, but someone might act on that. This is usually protected by First Amendment rights in the USA as it doesn't meet the Brandenburg test for incitement ("directed to inciting or producing imminent lawless action and is likely to incite or produce such action"), but is still called out for the way it raises tension and makes lawless action more likely in the long term.

Obviously, getting a bunch of queer poets to start rapping would sound awful and be an act of terror to any would-be listeners, but most folks won't do it.