The policy of the United Stares must be to never negotiate with terrorists, including both foreign AND domestic. To do so only encourages further activity that is contrary to the interests of the people.
The illegal insurrection in which heavily armed domestic terrorists took over a federal building by force in Harney County, Oregon is a Seditious Conspiracy as defined in 18 U.S. Code § 2384. As such, these terrorists must be arrested as soon as possible and charged to the full extent provided by the law.