Hours after the attack on the Capitol ended, a group calling itself the Last Sons of Liberty posted a brief video to Parler, the social media platform, that appeared to show members of the organization directly participating in the uprising. Footage showed someone with a shaky smartphone charging past the metal barricades surrounding the building. Other clips show rioters physically battling with baton-wielding police on the white marble steps just outside the Capitol. Before Parler went offline — its operations halted at least temporarily when Amazon refused to continue to host the networ...