The Silencers: Two complementary new books sound an alarm about liberal hostility to free speech.

The intense polarization of American life was captured in 2008 by then-presidential candidate Barack Obama, a product of Chicago’s big-city pugilistic politics. Referring to the Republican opposition, he told a Philadelphia fundraiser that “if they bring a knife to a fight, we bring a gun. Because from what I understand folks in Philly like a good brawl. I’ve seen Eagles fans.” In The Intimidation Game: How the Left is Silencing Speech, Kimberly Strassel, a Wall Street Journal columnist, shows that Obama’s rhetoric was more than just a metaphor. Strassel presents a richly reported account of the political weaponry Obama and his allies have used to silence their conservative foes.