There could a possibilty here that Bush is secret contact with this guys and they are working together. Bush might be very well asking them to make these statements to send cues to North Korea and too see their response. Having them make these statements in a public way and not from a offical agent of the US govt certaintly is helpful to gauge the situation without escalating the situation diplomatically. Its just a thought
I doubt Bush is using Walter Mondale as a bag man.