I’d say that flashmobs (which are “meet here at...” announcements sent by phone text) are more of a tool of the left.
Some think that they are “spontaneous” public “events” but I suspect that it has ties to anarchists who like to “test the wires” to see that a “mob” can be quickly paged to an address (as cover or to appear to be support for the anarchists activities).
You are correct. I live near a bunch of pagans and have heard them talk about how happy they are to answer the call and pour out into the streets. This is one of their tools, why should we not use it as well?