Yes, what the host allows to be said will reflect on him (or her, or it as the case may be).
But that’s a slightly different point. If Roeder advocated violence on the Op. Resc. boards (and was not deleted), then that is definitely a point against them (again, I don’t know if he did or not). But if he merely posted messages opposing abortion; then, one day, kills someone… the “connection” between him and the organization is less substantive.