It’s no secret that far-left domestic groups linked to foreigners are sowing chaos and hate on American streets and meddling in US elections. But these outfits have managed to keep their funding details hidden, even as they enjoy tax breaks. Good for House Republicans for fighting to expose them, end the outrageous breaks and uncover any unlawful activity here. This week, the House Ways and Means Committee set a hard Oct. 20 deadline for three groups in particular — The People’s Forum, BreakThrough News and Tricontinental — to comply with congressional subpoenas for info on their “fiscal sponsorships involving foreign...