the assumption appears to be that intelligent life would wish to expand. the expansion drive makes sense for purely biological life as it arose by natural evolution, technologically advanced life isn't going to stay purely biological for long however.

interstellar expansion is going to be a huge hassle, at a minimum you are going to be mass constrained and require a long period of investment in fuel (such as antimatter production) during which your competitors that chose to stay in the solar system will gain an edge and may strike before you leave. there isn't going to be MAD in space once you no longer rely on your planet of origin for anything truly important.

we should actually be deeply worried about the space race, because the early adopters will be making nukes out there and may come back to yank up the ladders.