These policies, at least those I'm aware of, have fixed benefit levels both for legal fees and civil judgements. Like property or more comparable liability insurance. The companies liability isn't unlimited, and statistics of violent incidents exist. And yes, I'd presume if the current climate of left wing violence continues rates might go up. In the short term, the expanding base of potential customers might limit that.
Yes, the question is the likelihood of a claim (absent law enforcement). Fire insurance depends on things like proximity of hydrants and whether your fire department is paid or volunteer; I’d think this poses similar risks.