There are ways. The first thing to recognize is the extent to which they operate off other people's money. They is their vulnerability.
In Wisconsin, a good first blow was landed by the Republicans in prohibiting mandatory dues withholding for public employee unions. Given a choice, public employees don't like the idea of sending in union dues. This cripples the union's activism.
A second thing would be to figure out how to eliminate the network of "non profit" organizations that the left uses to get their activism done. One way would be to just simply eliminate tax deductions for giving to non-profits.
“The first thing to recognize is the extent to which they operate off other people’s money. They is their vulnerability”
You should repeat this post often—it is important that people focus on a few critical goals in the fight for freedom. First is to diminish their flow of funding. Identify the supporters and put on the public pressure. Second, information is the fuel, not money—money is only useful to the extent it can generate and control the information that people receive. There must be multiple information sources that share information about freedom. Currently, nearly all information sources are controlled by socialists. That culture took years to create and it has to be turned around—education and children are important to this goal.