The ACLU is no friend of the Trump administration. Yet it is under fire for having defended the First Amendment rights of the organizers of last weekend's rally in Charlottesville. One charge is that the ACLU gives "free legal support to hate-based causes" while doing too little to protect progressives. Another is that it underestimates the impact of cyberbullying in its defence of the precept that "speech cannot do real damage." The most ominous indictment is that the ACLU "perpetuates a misguided theory that all radical views are equal." If by radical we mean willingness to engage in political violence, the "theory" is neither misguided nor antiquated. In an era of political polarization, it is indispensable.