Frank Schaeffer, son of religious right leader Francis Schaeffer, talks about the radical rhetoric used by his father that got him invited to lunch with Republican presidents.

If there is a legitimate reason for the use of force [against the US government]... then at a certain point force is justifiable.

I looked at the part in the Christian Manifesto where Schaeffer talks about using force and to be fair he is talking about civil disobedience (protests, witholding taxes, etc) and he counsels against using violence.