Who on earth says they need or deserve a "public channel to express themselves"? The world seemed to get by just fine before social media existed, and I have no doubt we'd all be perfectly fine if it were gone tomorrow. If the white supremacists are stuck going back to physically mailing letters around and struggling to organize that's a net win for society...
Where exactly did you come to the conclusion they're expressing themselves peacefully? So far we've had the Capitol stormed, and a thwarted attempt at kidnapping and murdering a state governor. Neither of those two events are anything resembling "peaceful".